Superconducting Module & Test Facility (SMTF)

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The SMTF proposal is to develop U.S. Capabilities in high gradient and
high Q superconducting accelerating structures in support of the
International Linear Collider, Proton Driver, RIA, 4th Generation Light
Sources, electron coolers, lepton-heavy ion collider, and other
accelerator projects of interest to U.S and the world physics community.

> SMTF Institutions & Contact Persons:
>
> Argonne National Laboratory: *Kwang-Je Kim*
>
> Brookhaven National Laboratory: *Ilan Ben-Zvi*
>
> Center of Advanced Technology, India#: *Vinod Sahni*
>
> Cornell University: *Hasan Padamsee*
>
> DESY/TESLA: *Dieter Trines*
>
> Fermi National Accelerator Laboratory: *Robert Kephart*
>
> Illinois Institute of Technology: *Christopher White*
>
> INFN\*: *Sergio Bertolucci, Giorgio Bellettini and Carlo Pagani*
>
> KEK: *Nobu Toge*
>
> Lawrence Berkeley National Laboratory: *John Byrd*
>
> Los Alamos National Laboratory: *Patrick Kelley*
>
> Massachusetts Institute of Technology: *Townsend Zwart*
>
> Michigan State University: *Richard York*
>
> Northern Illinois University: *Court Bohn*
>
> Northwestern University: *David N. Seidman*
>
> Oak Ridge National Laboratory: *Stuart Henderson*
>
> Stanford Linear Accelerator Center: *Chris Adolphsen*
>
> Thomas Jefferson National Accelerator Facility: *Swapan Chattopadhyay*
>
> University of Pennsylvania: *Nigel Lockyer*
>
> University of Rochester: *Adrian Melissinos*
>
> University of Wisconsin: *David Larbalestier*

\*: INFN is discussing its possible contribution to SMTF. 

#: Center of Advanced Technology, India has expressed interest in
collaborating as a member institution. The detail of the participation
is being worked out between Vinod Sahni and Fermilab.

Table of Contents

1.  Executive Summary

2.  Introduction

3.  International Superconducting Radio Frequency (SRF) Activities

4.  [ILC Test Facility]{.underline}

    a.  RF Power for the ILC Test Facility

    b.  High Gradient Cavities

    c.  Accelerator Physics Studies for the β =1 modules

5.  [Proton Driver Test Facility]{.underline}

    a.  325 MHz Pulsed RF Systems for β\<1 Test Area

    b.  Program sequence for the 325 MHz Pulsed Linac β\<1 Test Area

6.  [CW Test Facility]{.underline}

    a.  Applications for cw SRF in accelerator-based facilities

    b.  Goals for a cw SRF test facility at SMTF

    c.  Prototype cw cryomodules for SMTF

    d.  Infrastructure requirements for a cw SRF test facility

7.  [RIA Test Facility]{.underline}

8.  Electron beam: Fermilab/NICADD Photo Injector and Upgrades

9.  Cavity and Cryomodule Fabrication Infrastructure

10. SMTF Facility

    a.  Meson East Infrastructure

        i.  Space in Meson Hall

        ii. Conventional Facilities in Meson Hall

        iii. Technical Infrastructure in Meson Hall

    b.  Cryogenics for the SMTF

11. Generic Accelerator Physics

> a\. Potential applications of an electron beam at SMTF: R&D for ILC
> and advanced accelerator physics

a.  b\. SRF Materials R&D at SMTF

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12. Cost and Schedule

13. SMTF Organization

    a.  International Collaboration on SMTF

14\. Summary

1\. Executive Summary

This proposal describes a new US initiative to establish a
superconducting radio-frequency (SRF) accelerator facility at Fermilab.
The facility would provide the primary development and testing forum for
major SRF-based projects in high energy physics, most notably the
International Linear Collider (ILC) and Fermilab Proton Driver (PD) at
Fermilab, as well as complement the existing and planned SRF facilities
at other laboratories for nuclear physics, materials, and life sciences.
Superconducting radio frequency cavity technology has advanced greatly
in the past decade, so much so that an international panel recently
recommended adopting SRF technology to accelerate the electron and
positron beams of the International Linear Collider. In fact, nearly all
new initiatives for electron, ion and proton sources incorporate
superconducting cavities. These projects place increasing demands on the
performance of SRF, and on the ability to produce SRF components in
large quantities at lower costs. This challenge has not yet attracted US
industry, because of the high initial investment cost in the technical
infrastructure, and in training an expert work force in cryogenics and
materials processing. By creating a shared infrastructure, the
collaborators would benefit from the oversight and resources of a major
laboratory, would avoid needless and costly duplication of resources,
and would create the sort of scientific synergy that would assure
success.

The centerpiece of this proposal is the *Superconducting Module and Test
Facility*, or *SMTF*, that would be located at Fermilab, and that would
provide test areas with cryogenics, high-power RF sources, beams and
other required infrastructure for operating and testing a wide range of
superconducting modules (cryomodules), along with a prototype factory
for assembling SRF modules of various types. The largest of these test
areas would have electron beam capability to allow full evaluation of
cryomodule performance, and would support an ongoing program of beam
dynamics studies. Institutions involved in the ILC, the Rare Isotope
Accelerator (RIA), improvements to existing or planned electron beam
accelerators and storage rings, the Fermilab Proton Driver, high-energy
electron cooling and various fourth-generation light sources have all
expressed strong interest in using such a facility and in working
together on the development of their SRF systems.

The SMTF is not meant to replace infrastructure and capabilities that
already exist or are planned at other U.S. laboratories and
universities, but to expand R&D capabilities in an efficient manner to
meet increasing demands. In particular, it is envisioned that one of the
test areas would essentially be dedicated to testing the 1.3 GHz
cryomodules that are required for both the ILC and the Fermilab Proton
Driver. In this proposal, it is assumed that Fermilab would be the
central laboratory for coordinating the ILC development of these
components in the U.S. and would manage a collaboration of universities
and laboratories (e.g., Cornell and JLab) and international ILC members
(e.g., DESY and KEK) and industrial partners to develop the capabilities
in the U.S. to build high performance cryomodules, which are presently
built only in Europe.

The cavity development program for the other SRF projects would be led
by collaborating institutions and projects, although there would be
sharing of infrastructure to reduce costs. The programs and operational
priorities at SMTF would be directed by an Institutional Board modeled
on those successfully used for large particle physics collaborations
(eg. CDF) and the TESLA Test Facility (TTF) at DESY. This board, which
is now assembled, has representatives from the member institutions and
the various SRF projects. There would be two co-spokespersons of this
board that would act as leaders of the collaborating institutions in
scientific and technical considerations related to the design,
construction and operation of SMTF, and would represent the
collaboration to all supporting funding agencies. The actual operation
of SMTF, including the associated cavity and cryomodule development
infrastructure, would be managed by FNAL. Formal MOUs would be developed
between Fermilab and the participating laboratories and universities for
these programs. Strong international cooperation and involvement at SMTF
is anticipated with DESY, the TESLA collaboration, INFN, KEK, India, and
others.

It is proposed that the SMTF would be constructed in phases beginning in
2005 and proceeding through the end of the decade. These phases would
correspond to expanding the testing capabilities and SRF development
infrastructure at FNAL. The initial tasks include the clean-up of the
Meson East area and the establishment of the test areas, each with
appropriate shielding, cryogenic capability and AC power for the RF
sources. Also, the current A0 photo-injector at FNAL would be upgraded
and moved to the ILC test area. For the ILC program that is proposed,
the final assembly of the cavities into cryomodules would take place in
clean room facilities constructed at Fermilab that would also support
other projects, including SRF materials research.

Some of the program goals of projects that would use SMTF are listed
below:

1)  International Linear Collider (ILC):

    a.  Establish a high gradient, 1.3 GHz cryomodule test area at
        Fermilab with a high quality pulsed electron beam using an
        upgraded A0 photo-injector.

    b.  Establish a factory with infrastructure for the assembly of
        prototype cryomodules using cavities produced at collaborating
        institutions and industries.

    c.  Fabricate 1.3 GHz high gradient prototype cryomodules in
        collaboration with laboratories, universities and US industrial
        partners. Test cryomodules and other RF components as
        fabrication and operational experience are acquired and designs
        are optimized.

    d.  Demonstrate 1.3 GHz cavity operation at 35 MV/m with beam
        currents up to 10 mA at a ½ % duty factor. Higher currents or
        duty factors may be explored if the need arises, but are beyond
        the present scope of the proposal.

    e.  Develop the capability to reliably fabricate high gradient and
        high-Q SRF cavities in U.S. industry.

2)  Proton Driver (PD) Low Beta (β \< 1) Cavity Program

    a.  Fabricate test structures and cryomodules for Proton Driver
        applications.

    b.  Establish an area for high power, 325 MHz, RF testing of β \< 1
        accelerator structures in pulsed mode (\~1% duty factor).

    c.  Demonstrate operation at 27 MV/m with beam currents up to 8 mA
        at ¾ % duty factor. Higher currents or duty factors may be
        explored if the need arises, but are beyond the present scope
        considered in this proposal.

    d.  The Proton Driver also uses β=1, 1.3 GHz cavities cryomodules
        that would be nearly identical to those for the ILC. There would
        be a significant overlap in ILC and PD R&D activities in this
        area.

3)  CW:

    a.  Fabricate the highest attainable Q-value cryomodules with
        emphasis on accelerator and deflecting cavities.

    b.  Establish a test area with pulsed beam availability that will
        extend the reach of the present U.S. program in CW capabilities.
        This area will make use of the β=1 pulsed test beam. Possible
        low current CW beams may be considered in the future (high
        current CW beams are available elsewhere).

    c.  Demonstrate 20 MV/m CW cavity operation with Q values of \~
        3x10^10^ for light source applications, with associated RF
        controls.

4)  Rare Isotope Accelerator (RIA) Production Facility:

    a.  Clean and cold-test individual cavities after chemical
        processing.

    b.  Clean and assemble cavities into cavity strings, forming a
        sealed unit including RF couplers, beam line valves, and vacuum
        manifold and valves.

    c.  Assemble cryomodules incorporating the cavity strings.

    d.  Cold test and high power test assembled cryomodules.

5)  Accelerator Physics and SRF R&D

    a.  Construct and operate an improved photo-injector that would
        provide beam for the β = 1 and CW module tests and be the
        centerpiece of continuing beam physics program for understanding
        and improving all types of facilities based on electron linacs,
        and the training of accelerator scientists.

    b.  Begin a program of R&D on high-gradient and high-Q SRF cavity
        design and construction.

    c.  Establish a program of SRF material research to improve cavity
        performance.

The proposal presented in the following sections outlines an R&D program
for the next 8 years including cost and schedules (FY05-FY12). The
budget has been planned with the understanding that the infrastructure,
ILC and PD components and operation is managed by Fermilab. The
component budget for RIA and CW areas are the responsibilities of the
lead laboratories for these projects. The budget has been divided into
the SMTF infrastructure part, the component parts for the four proposed
areas and the operation of the facility. The operations budget includes
support for training young scientists and engineers, who will be
essential for the next generation of accelerators. The budget estimates
are \$23M for the infrastructure, \$18M for the International Linear
Collider, \$6M for Injector Upgrades, \$16M for Proton Driver, \$2M for
Rare Isotope Accelerator cavity testing, \$9M for CW cavity research and
finally, \$22M for operations over a 8 year period.The requested M&S
funds is \$96M. Contingency has been estimated to be 10% on the
operational costs and 25% on all other M&S costs for a total estimated
contingency of \$20M. The total requested fund is \$116M. The estimated
personel for SMTF infrastructure is 149 FTE-years, 622 FTE-years for
operations, 80 FTE-years for ILC, 30 FTE-years for the injector, 26
FTE-years for CW, 7 FTE-years for RIA, and 88 FTE-years for proton
driver. The estimated FTE-years needed over all areas and operations is
\~1000. The total budget includes the RIA hardware budget and FTE
requested from SMTF at Fermilab. The RIA specific cost, such as the cost
of cryomodules etc., is not included in the SMTF total budget.

The schedule in this proposal extends through 2012 because we expect
that SMTF will be an important facility for the ILC project to proceed
on the schedule as presently envisioned by ICFA. The facility will be
necessary in the initial stage of the industrial production of
cryomodule and associated components.

2\. Introduction

A variety of projects are being planned in particle physics, nuclear
physics, and fields of basic energy sciences such as condensed matter
physics and biological physics that propose to use SRF linac technology.
These projects are distributed across many of the major US laboratories
funded by DOE and NSF. We propose to construct a SRF cryomodule and test
facility (SMTF) in the meson area at Fermilab. A medium energy electron
beam and a low energy H^-^ beam would permit a unique opportunity for
characterization of the properties of superconducting RF cavities and
for beam-related experiments. The members of the team are from a
consortium of several US and international laboratories and
universities.

We list several possible future projects that use RF Superconductivity.

1)  International Linear Collider (ILC)

2)  The Rare Isotope Accelerator (RIA) (located at Argonne or MSU)

3)  Proton driver at Fermilab or BNL.

4)  Upgrades (12 GeV) to Jlab electron linac, the extensions of the FEL
    and the proposed ELIC (Electron Light Ion Collider)

5)  SNS (Spallation Neutron Source) upgrades to higher beam power \~ 4
    MW.

6)  Fourth generation light sources at ANL, BNL, Cornell, JLAB, LBNL,
    and MIT using SRF linac technology for ERLs (energy recovery linacs)
    or FELs (free electron lasers).

7)  Brookhaven plans to use ERLs for electrons colliding with RHIC heavy
    ion beams (E-RHIC) and for electron cooling of the RHIC beams.

These projects have common or similar RF systems and require development
that would benefit from a coordinated effort among the laboratories.
Several of the laboratories have infrastructure to carry out SRF
development but have limited fabrication capabilities. The current
efforts in SRF are broadly funded by USDOE HEP, Nuclear, Basic Energy
Sciences and the NSF. Many of the above projects would benefit from a
cryomodule test facility with beam capabilities, which is presently not
available in the US. We propose such a facility and refer to it as the
SMTF. It would fill the gaps in the existing SRF development
capabilities.

The critical tests that groups from the above projects could perform at
this facility include:

1)  Demonstrate for ILC 1.3 GHz cavity operation at 35 MV/m with beam
    currents up to 10 mA at a 1/2% duty factor in four cryomodules with
    8 cavities each.

2)  Demonstrate for CW applications 20 MV/m cavity operation at Q values
    \> 3E10 and develop accelerating and deflecting cavities.

3)  Demonstrate for the Proton Driver 1.3 GHz, β \~ 0.5-0.8, elliptical
    cavity operation at \> 15 MV/m at Q \> 5E9 and a 1% duty factor with
    multiple cavities being driven by one klystron.

4)  Demonstrate for the Proton Driver and related applications high
    gradient operation in pulsed mode of 1.3 GHz and 325 MHz,     β \< 1
    cavities and cryomodules.

5)  Demonstrate individual cavity resonance control with multiple
    cavities driven from one klystron, using fast ferrite phase
    shifters, at both 1.3 GHz and 325 MHz

6)  Demonstration of RIA cavities and cryomodules.

These demonstrations encompass research and development topics critical
for the continued iteration and evolution of SRF linac systems, for the
development of cost effective low to medium β linac sections needed for
proton/ion linac, and development of lower power cost (driven by
refrigeration costs) CW operation for the many upcoming light source
applications and for the future ILC.

This proposal is developed in collaboration with Jlab. Jlab has
submitted a SRF Accelerator Science and Technology proposal to DOE
Office of Science in FY 2004. Every effort has been made, via mutual
collaborative efforts between the two proponents to make the two
proposals as complementary as possible. A joint document between
Fermilab and JLab is being developed to address these two proposals.

Similarly KEK is also developing a Superconducting Test Facility (STF)
proposal to be submitted to the funding agencies in Japan for the
International Linear Collider R&D. KEK is also a collaborator on the
SMTF proposal. We have developed this proposal in collaboration with
DESY and KEK with the common goal of R&D and industry involvement in
each region with the goals of reducing the cost and advancing the SRF
technology.

Thus the SMTF goals are to:

-   Design, fabricate and test SRF cryomodules and associated systems

-   Provide infrastructure for cryomodule and linac systems test

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-   Collaborate on SRF technology development including industrial
    collaboration

Proposed SMTF Plan

We propose to develop the meson east area at Fermilab into a cryomodule
test area. The document is organized around the four main SRF areas: the
1.3 GHz, β=1 ILC Cryomodule test facility, the CW test area for
next-generation CW light source, and the β \< 1 test area for PD, and
the RIA facility. These R&D activities will operate under a shared
infrastructure of the Meson cryogenic facility, pulsed RF and modulator
power sources, controls, safety and technical support.

The allocated space should be able to accommodate initially four test
areas. The high gradient pulsed work and the CW activities would be
located in a single 100-150 meter beam line. A second area would be
large enough to accommodate the 325 MHz β \< 1 cryomodule activities.
We anticipate four different communities using the facility. At the same
time these communities will have strong interactions to benefit all four
areas. One community will concentrate on 1.3 GHz pulsed high gradient
tests, such as needed for the ILC and Proton Driver. Another community
will focus on cryomodule operation needed for present and the fourth
generation light sources and other proposed applications that use high
Q, CW operation. The third and fourth communities will emphasize β \< 1
activities at various RF frequencies. We envision that the regions will
initially operate in two different modes. In one region, physicists
would perform high power cryomodule tests as well as beam tests with a
medium energy electron beam (40 - 300 MeV). This is the energy of the
injector into the first cryomodule. We would also develop a beam
analysis section downstream of the cryomodule. In the parallel region,
tests (initially without beam) could be ongoing with low β demonstration
cryomodules. Shielding between the two regions will be necessary for
flexible operation. The details of the layout are presented in section
10.

The electron beam test area in SMTF would consist of an electron beam
injector, a beam analysis region after the injector and before the
cryomodules in order to measure incoming beam properties, a section of
four cryomodules, which constitutes two ILC RF units (defined later),
and space afterwards to evaluate the outgoing beam properties. The CW
activities are located downstream of the ILC cryomodules. The existing
FNPL would be an appropriate initial source. To achieve 40-300 MeV will
require upgrades to the source as described in section 8. This consists
of a gun and accelerating section, and is about 15 m (upgraded
eventually to 25 m) in length. We estimate that 20 m of beam analysis
space is needed to measure beam properties, followed by space for four
12 m cryomodules, and an additional 20 m of analysis space for the
outgoing beam and a beam dump, for a total of 100-150 m.

The cryogenics plant in the meson area needs to be upgrade as described
in section 10. We propose a two step approach. For the first step we
make minimal modifications to the existing infrastructure and utilize
what we can to supply the area quickly with about 60 Watts of
refrigeration at 2K. Each TESLA Test Facility (TTF) cryomodule (eight
9-cell cavities) consumes about 36 Watts of refrigeration at 2K. The
third step will requires a new refrigeration plant that can handle \~300
Watts. Medium energy electron beams will be used for testing the
cryomodules in the area and dark currents should be expected from the
cavity modules, therefore the appropriate radiation shielding will be
necessary.

To get started quickly we propose to initially use an eight cavity
cryomodule from DESY of the type being produced for TTFII. In parallel,
we would aggressively move to construct cavities and cryomodules in the
US. KEK will provide cavities to be tested inside this ILC cryomodule.
We note that US industry considerably lags European industry in SRF
technology and our plans would help correct this situation. This is
especially desirable given the large number of SRF projects in the US,
and the large scale of the ILC. We also note that significant
infrastructure exists at US laboratories but will also need upgrading.
We plan to incorporate existing infrastructure and expertise at US labs
and universities as well as US industry to build cavities, carry out
bare cavity tests in vertical Dewars, perform dressed cavity horizontal
tests, and assemble cavity strings and cryomodules. In addition we would
build couplers and tuners and other cryomodule components to extend the
full range of expertise and technology required for the major projects
envisioned.

In Phase I it is expected that ILC-Americas, Proton Driver, RIA, CW and
β \< 1 interests will launch independent but collaborative activities to
build cryomodule(s). Individual laboratories are assuming responsibility
for major subsystems and pre-testing efforts. The proposal is that, with
coordination from the ILC-Americas collaboration, Fermilab will lead the
effort of fabricating and testing the ILC cryomodule. Fermilab will also
lead the effort of fabricating and testing the PD cryomodules and ANL
will lead the RIA cavities testing and production work. The leadership
of CW cryomodule fabrication for light source applications is not yet
established.

This document is organized around the four main SRF areas: ILC, CW,
Proton Driver and RIA programs. Even though we present the four research
concentrations separately for ease of reading, the resources and goals
significantly overlap. Each area will benefit from the collective
effort.

3\. International SRF Activities

This section is a summary of the worldwide accelerator projects based on
SRF together with a short description of the expertise and
infrastructure developed for their success. Many of the laboratories
involved in these projects are SMTF collaborators who plan to use the
advances in SRF technology to launch new accelerator projects, also
briefly described. SMTF activities and the test facility will play
important roles in realizing future projects.

Superconducting cavities have been operating routinely in a variety of
accelerators with a range of demanding applications. With the success of
completed projects, niobium cavities have become an enabling technology
offering upgrade paths for existing facilities, and pushing frontier
accelerators for nuclear physics, high energy physics, materials and
life sciences. With continued progress in the basic understanding of
superconductivity, the performance of cavities has steadily improved to
approach theoretical capabilities, giving rise to a large number of
exciting new applications.

Superconducting linacs providing precision beams of heavy ions have
consistently been one of the most successful applications. At Argonne
National Lab, ATLAS has been operating for more than 25 years as a
national user facility for heavy-ion nuclear and atomic physics
research, logging over 100,000 beam-on-target hours of operation.
Besides the pioneer accelerator at Argonne, eight heavy-ion accelerator
facilities have operated or are still operating at Stony Brook, U. of
Washington, Florida State U, Kansas State U., JAERI (Japan) ALPI (Italy)
ANU (Australia) and the Saclay heavy ion linac. These utilized over 270
resonators made of niobium or lead-on-copper. These accelerators provide
beams with mass up to 100 atomic units and energies up to 25 MeV per
nucleon. New heavy-ion accelerator facilities utilizing superconducting
structures are near completion at Sao Paolo (Brazil), New Delhi and
Bombay. TRIUMF in Canada is upgrading ISAC with a superconducting heavy
ion linac to ISAC-II facility with a final energy to 6.5 MeV/u and mass
range up to 150.

At the frontier of nuclear science, CEBAF at Jefferson Lab in the USA
has been one of the largest SRF installations. Superconducting cavities
offer special advantages to electron accelerators for nuclear physics in
the 1 to 10 GeV range: high average current, low peak current,
continuous beam, and excellent beam quality. Construction finished in
1993 with installation of 380 cavities. Originally designed for 4 GeV,
CEBAF achieved beam energy of 6.5 GeV in five recirculating passes with
a CW beam current of 200 μA. Over a period of a few years, CEBAF
upgraded their in-line accelerating gradient from the design value of 5
MV/m to more than 7 MV/m. CEBAF operates for more than 5000 hours per
year. By now they have accumulated more than 2000 cavity-years of
automated operation. Plans are underway to raise CEBAF energy to 12 GeV
with the installation of 10 higher gradient cryomodules, now under
construction.

High-energy physics benefits from colliding beam storage rings of
steadily increasing energies. Because energy loss increases as the
fourth power of the beam energy (in circular machines), the electron and
positron storage rings need high gradient CW superconducting cavities
for reaching high energies. The colliding beams facilities that use(d)
SRF are (were) TRISTAN at KEK in Japan, LEP-II at CERN in Switzerland,
and the electron-proton collider HERA at DESY in Germany, as well as
high current, high luminosity machines CESR-III in the USA and KEK-B in
Japan. LEP-II at CERN in Europe has been the largest SRF installation.
CERN installed a total of 465 meters of SRF cavities to provide more
than 3.6 GeV reaching the highest energy electron-positron collisions:
208 GeV in the Center-of-Mass before LEP-II shut down for installation
of the LHC. Instead of using bulk sheet niobium cavities, CERN developed
a unique approach for LEP-II: to sputter a thin film of niobium on to a
copper cavity. LEP-II upgraded the in-line performance of their cavities
from 6 to 7.2 MV/m by successful high-field conditioning with both
pulsed and continuous RF.

With 14 TeV in the CM, the LHC at CERN will keep pace with the
historical rate of energy growth for proton accelerators.
Superconducting cavities and cryomodules are ready for LHC. At 400 MHz,
16 Nb-Cu cavities in 4 cryomodules will provide 16 MV per beam and will
deliver about 180 kW of beam power.

Electron storage rings as x-radiation sources have enormous impact on
materials and biological science. At Cornell, CHESS has been operating
as a parasitic light source with CESR for two decades. After replacing
the CESR copper RF system of 20 cells by a superconducting RF system
with 4 cells, the beam current was increased from 300 mA to 750 mA, and
accordingly the radiation flux. Cornell has transferred the technology
of CESR cavities to ACCEL company in Germany which is providing turnkey
systems for major storage ring light sources around the world. Such
systems will be used in the Taiwan Light Source, the Canadian Light
Source and the DIAMOND light source in England. BEPC in China and the
Shanghai Light Source envision using SRF based on the KEK-B system.
Saclay-CERN collaboration developed a 350 MHz Nb-Cu SRF system for
SOLEIL in France.

A 3^rd^ harmonic (1.5 GHz) SRF system allows bunch lengthening, decrease
of charge density & increase of beam lifetime. After installation of
such systems, both SLS in Switzerland and ELETTRA in Italy gained a
factor of 2 on beam life-time. BESSY in Germany is preparing to install
a 3^rd^ harmonic SRF cavity.

The characteristics of x-rays produced by a synchrotron radiation (SR)
source are limited by the qualities of the stored electron beams. The
superconducting linac based Energy Recovery Linac (ERL) is a different
approach to producing high quality electron beams. Electrons are not
stored, so constraints of beam equilibrium in a storage ring are not a
limit. Photo-injectors achieve bunches with emittances, shapes, and
length superior in important ways to bunches in storage rings. A CW
superconducting linac accelerates bunches to high energy while
preserving the salient beam characteristics. After acceleration,
superior high energy bunches pass through undulators to produce SR beams
with unprecedented characteristics. After producing SR, the electrons in
an ERL re-enter the linac, but 180º out of accelerating phase. These
bunches are then decelerate and yield their energy back to the linac
electromagnetic field. The energy recovered by the linac accelerates new
electrons. The emerging low energy beam is deflected into a beam dump.

A Cornell/JLab collaboration has proposed an energy recovering SRF linac
operating at energy of 5-7 GeV and an average current of 100 mA. To
address many important accelerator physics issues of the injector and
the main linac, there is a proposal for a small scale prototype ERL at
100 MeV and 100 mA. Daresbury (UK) has started construction on a
prototype for its Fourth Generation Light Source (4GLS) project, a 600
MeV, 100 mA energy recovery linac driving a suite of light sources to
generate radiation in the 3 - 500 eV range (IR to XUV). KEK is
considering a 2.5 - 5 GeV, 100 mA ERL light source along the design of
the Cornell ERL. BNL is exploring luminosity upgrades to RHIC by using
high current (100 -- 300 mA) electron beams from an ERL to cool the RHIC
beam.

Free Electron Lasers (FELs) are sources of tunable, coherent radiation
at wavelengths covering a wide range from mm to the vacuum UV and soft
X-rays. SRF-driven FELs have reached unprecedented values of wavelength
and average output power. The first FEL beam was demonstrated nearly two
decades ago with a 50-MeV beam from the SCA at Stanford. The Jefferson
Lab IR FEL has "lased" in the 1-6 μm wavelength range and reached
average output power of 10 kW, the highest CW average power ever to be
achieved. JLab also demonstrated energy recovery with more than 99.8%
efficiency. Nearly one MW beam power was energy recovered. This is an
important milestone toward high beam power Energy Recovery Linacs of the
future. Other CW FEL projects underway are at JAERI in Japan and at
Darmstadt in Germany and ELBE at Rossendorf.

At ultra short wavelengths, less than 100 nm, mirrors are not available
for FELs which must be based on the SASE principle,
Self-Amplified-Spontaneous-Emission. The Tesla Test Facility (TTF) at
DESY has a dual purpose. (1) To demonstrate a high gradient SRF linac to
prepare the superconducting technology for the International Linear
Collider and (2) To advance the science of SASE while providing UV to
x-ray beams to a user facility. TTF has lased over a wavelength range
from 80 nm to 180 nm, corresponding to a beam energy between 181 and 272
MeV, to demonstrate SASE saturation at the wavelength of 98 nm. An
upgrade to one GeV is underway. The German government has agreed to
supply partial funding for a European X-ray FEL at DESY\
with the capability of reaching the one Å wavelength range. Other
European labs are soliciting their ministries for the remaining
financing.

There are several studies in progress for future X-ray FELs. Many
concepts are based on an evolution of high gradient technology for the
linear collider. Lawrence Berkeley National Lab is developing the Laser
Based Ultra-Fast X-Ray Facility (LUX) to produce femtosecond x-ray
pulses with high flux, and repetition rate matched to the requirements
of structural dynamics experiments. The 2.5 - 3 GeV machine is based on
a 1300 MHz SRF 4-pass recirculating linac for acceleration of electrons
(average current 10uA) produced by a high-brightness photocathode RF
gun, at a bunch repetition rate of approximately 10 kHz. MIT is studying
an X-ray laser facility to span a broad range of wavelengths from the
ultra-violet to the hard X-ray region using fundamental and third
harmonic, generation. The accelerator configuration would include a
staged superconducting electron linac from 1 to 4 GeV, multiple
undulators and beam lines. BESSY in Berlin proposes a single-pass 1.5 --
2.2 GeV FEL for wavelengths between 63 and 1.2 nm.

Stimulated by the success of SRF technology around the world, the
Spallation Neutron Source under construction at Oak Ridge switched to
SRF in 2000. Neutron scattering is an important tool for material
science, chemistry and life science. The SNS at Oak Ridge National Lab
will be an advanced pulsed spallation source with 1.4 MW of beam power
at the target, upgradeable to 5 MW. This would correspond to the average
flux of the highest flux reactor at Grenoble. From 200 MeV to 1000 MeV,
800 MHz SRF cavities will drive the SNS linac. As one of the partner
labs, JLab is responsible for linac design and construction. There will
be a total of 81 (one meter-long) cavites operating at 804 MHz. Eleven
medium-beta (0.64) cryomodules have three cavities each and 12 high-beta
(0.81) cryomodules will have four cavities each. Performance above
design specifications has been achieved for the bare cavities and
cryomodules.

The highest priority for a major new facility in the Long Range Plan of
the US Nuclear Science Advisory Committee is the Rare Isotope
Accelerator, RIA. There will be two major sections to RIA, a
superconducting multi-ion multi charge-state driver linac spanning
nearly the entire range of masses from protons to uranium and particle
velocities, 0.02 \< β \< 0.84, and a superconducting post accelerator of
efficient acceleration and transmission of multi charge-state rare
isotopes. In Europe, SPES and EURISOL are RIA type facilities also under
study.

Future spallation neutron sources, neutrino beam lines, neutrino
factories and muon colliders place a heavy emphasis on developments in
high intensity proton linacs and relevant superconducting accelerator
technologies. Fermilab, CERN and Brookhaven are studying high intensity
proton linacs for multi purposes. As discussed in this proposal, the
Fermilab 8 GeV superconducting linac could supply the Main Injector to
produce super beams for neutrinos and intense beams for anti-proton
production, or the linac could directly produce muons and spallation
neutrons. CERN is studying a multi-purpose SRF proton linac (SPL) for a
super neutrino beam, a possible neutrino factory, as well as to upgrade
the injector chain for the LHC, and to produce heavy ion radioactive
beams for nuclear physics. Using SNS cavity technology at twice the
frequency, a 1.2-GeV SRF linac for a 1-MW AGS upgrade at BNL aims to
increase the AGS beam power by a factor of 10 in order to produce
intense neutrino beams and for other applications.

For the future high intensity proton accelerators could play a major
role in Accelerator Based Transmutation of Waste (ATW). Spallation
neutrons transmute long-lived actinide isotopes and fission products to
stable isotopes, or to isotopes that decay to stable products over 100
years. This approach can lessen the technical problems of storing
long-lived high level radioactive waste. In an optimistic design, a
single accelerator can burn the waste from ten 1 GW reactors, while
providing enough power to run itself.

A European consortium is studying XADS, a 10 mA CW, 600 MeV (tunable)
proton linac based on SRF technology developed in earlier national
projects (ASH, IPHI, TRASCO, ESS, and CONCERT) JPARK in Japan is
developing a 200 MeV SC section to upgrade energy for future ADS
applications. The Korean Multi-purpose Accelerator Complex KOMAC at
KAERI is studying a one GeV 20 mA linac for waste transmutation, medical
therapy and industrial applications. There is a similar Indian ADS
program at Center for Accelerator Technology (CAT) in Indore.

Extensive SRF infrastructure exists worldwide for cavity fabrication,
surface treatment, clean assembly, cold testing, cavity string assembly,
and final cryomodule assembly before accelerator installation.
Substantial infrastructure exists in US Laboratories and will be used
for the module activities of SMTF.

In general, cavity production facilities include eddy current scanning
machines for material inspection, hydraulic presses for deep drawing
cavity half-cells, digital control milling machines for precise trim
machining, and large electron beam welders for finished structures.
Final tuning and inspection systems consist of automated tuning machines
and co-ordinate measuring machines. Cleaning facilities include open and
closed cavity etching systems, electropolishing set-ups, high purity
dust free water systems, and high pressure (100 atmospheres) water
rinsing. UHV furnaces purify cavities at 1350 C under high vacuum. Test
setups include radiation shielded pits and bunkers, cryostats, and
cryostat inserts, multi-hundred watt CW RF power sources and MW class
pulsed klystrons for high power operation and high pulsed power
processing. Test systems are supported by refrigeration to 2 K. There
are large Class 10 - 100 clean rooms for cavity and cavity-string
assembly. Cryomodule assembly areas are equipped with major survey,
support and alignment tools.

Major facilities for all the necessary operations are available at DESY
and Jefferson Lab. CERN, INFN, Saclay, KEK, Cornell, Los Alamos, ANL,
and Fermilab have comprehensive facilities that cover many (but not all)
of the stages. Several industries around the world have installed
significant capability to cover various stages. Most of these industries
are in Europe and Japan.

These facilities have been used to build cavities and cryomodules for
TRISTAN, HERA, CEBAF LEP-II, CESR, KEK-B, FELs, ATLAS, SNS and the TESLA
TEST FACILITY. Major facilities for low velocity accelerators are
available at INFN, ANL, Michigan State University, and Los Alamos
National Lab. SMTF plans to use the facilities in the US to fabricate
cryomodules at Fermilab in conjunction with developing the capability of
industry.

4\. ILC Test Facilities

This section describes the ILC program that will be based at FNAL and
the associated facilities at SMTF. In broad terms, the goal of this
program is to build at least four ILC cryomodules (8 cavities per
cryomodule) in the next several years that meet performance
requirements. This work would proceed in phases as outlined below and is
illustrated in Figure 4.1. The ILC and proton driver R&D associated with
the β=1 cryomodules have nearly complete overlap and therefore we
describe only the β\<1 R&D in the proton driver section. Fermilab relies
on ILC activities to address R&D issues associated with the β=1
cryomodules.

Prior to the formal start of SMTF activities in FY06, the SMTF-ILC
collaborators are beginning the fabrication of four ILC cavities in the
US. Work is beginning with KEK in defining the 4 cavities expected to be
delivered to Fermilab in FY06. Also, construction would begin on a
horizontal test stand, which is a cryostat that allows a single fully
dressed cavity to be operated with pulsed, high power rf. This test
stand would be located in the Meson East area and the construction of
the associated infrastructure would begin in FY05 as well. Finally, a
capture cavity that was recently acquired for the A0 photo-injector
would be commissioned to a gradient of 25 MV/m.

Phase One, FY06-FY08. The goal during this period would be to fabricate
two cryomodules. One of these, the ILC-cryomodule, would contain
cavities made in the US and Japan, and would be assembled at FNAL. The
other, the TESLA-cryomodule, would be the obtained from the DESY
collaboration although the degree to which the cavities and cryomodule
would be assembled when received is yet to be determined. Of these two
cryomodules, at least one would be tested with beam in early FY07. For
this purpose, the A0 photo-injector would be moved to the SMTF area. Its
initial configuration (Injector-A) would consist of a gun and two
capture cavities, which would allow for basic accelerator performance
testing (the Injector-B configuration in Figure 1 refers to the addition
of third-harmonic cavities for a beam dynamics program that has been
proposed with this injector - see the 'Accelerator Physics and SRF R&D'
section).

Phase Two, FY08-09. The second cryomodule would be installed and the
pair would be powered by a single 10 MW klystron. Subsequent iterations
to the cavities are envisioned to improve the performance of these
cryomodules. Construction would start on two additional cryomodules.

Phase Three FY09-11. Eventually four cryomodules, three built in the
U.S., would be installed and used to accelerate ILC-like beams. The
energy upgrade of the injector will likely occur in FY11-12.

A major objective of the US university/laboratory/industrial partnership
is to learn how to reliably fabricate high quality ILC cavities and
assemble them into cryomodules. This process would utilize the expertise
within the international ILC collaboration and would be an important
first step towards industrialization of cryomodule production as this
knowledge can then be efficiently transferred to large-scale
manufacturers. This process would be likely be necessary in all three
regions of the world that are collaborating on the ILC to produce the
large quantity 2500 (500 GeV) of cryomodules that are required.

![](media/image3.png){width="5.9944444444444445in"
height="7.656944444444444in"}**Figure 4.1 Phases of the ILC Test
Facility**

**Fermilab Activities in FY06-FY08:**

Activities at Fermilab in FY06-FY08 would include testing one cryomodule
with beam and upgrading the photoinjector. The first tests of dressed
cavities (i.e., with He vessels and couplers) would occur in the
horizontal test stand in FY06: the cavities received from KEK would
likely be tested first. These tests require a 2K helium supply, RF power
for a single cavity (up to 500 kW), and a low level RF (LLRF) drive
system.

During FY06, FNAL would prepare to receive dressed cavities built
offsite as described below. This would require completing the
infrastructure at Fermilab so that the ILC-cryomodule could be fully
assembled. The infrastructure needed to assemble a string of cavities,
primarily the class 10 clean room, should be ready for use in MP9 early
in 2006. The area where the string is assembled (300 mm support pipe,
super-insulation, etc.) into the \"cold mass,\" the materials to build
the cold mass and the infrastructure for inserting the cold mass into
the vacuum vessel would be ready as well.

The cryogenic plant for removing the expected heat load from one
cryomodule would be finished in FY06. The RF system, including the
klystron, modulator, waveguides, and controls, would also be ready for
use by the end of FY06.

A significant ramp-up by US industry would be required to produce
processed cavities (i.e., ones that been etched, baked and high pressure
rinsed to allow high field operation). This would take a few years and a
substantial investment since no US company is currently capable of
producing such cavities. In particular, considerable time and cost would
be required to deal with the complex environmental issues associated
with the chemical enchants that are required. Industry would be used to
assemble the cavities from stamped half-cells. This possibility is being
pursued as are discussions with JLab and Cornell on how to exploit their
capabilities in this area. If it becomes apparent that four cavities
cannot be fabricated in a timely manner (\~18 months), they would be
purchased from ACCEL, which is a German company that supplies most of
DESY's 'bare' cavities (i.e., ones that are not processed).

After eight cavities have been acquired (nominally four from KEK and
four from U.S. manufacturers) and assembled in a string, experience from
DESY indicates that the assembly into a cryomodule would require 3-4
months (with experience, the process should take only 3-4 weeks). The
goal would be to have a complete eight-cavity cryomodule that is ready
for testing by mid-FY07. In parallel, FNAL would be prepared to receive
a cryomodule from the TESLA Collaboration on the same time scale.

The A0 photo injector can be moved to the meson area for use once the
first cryomodule is assembled and it is ready to be energized. It is
assumed that this might be late FY07. By this time, the injector with
two capture cavities will be installed and ready for testing. Cryomodule
beam tests will be interspersed with the photo injector planned
upgrades.

The first ILC-cryomodule would be built on a \"best effort\" basis and
gradients in the 20-25 MV/m would be the initial goal. Under-performing
cavities and components would be replaced or upgraded as they become
available. The TESLA-cryomodule would be expected to arrive in FY07 and
the \"best\" cryomodule would be tested with beam. How the TESLA
cryomodule would be shipped to Fermilab is still being discussed as
there is a concern that shipping a fully assembled cryomodule might
damage its delicate components. Fermilab should have the ability by that
time to convert a cavity string into a full cryomodule, so perhaps
shipping the cavity string separately from the other components would be
more prudent.

**Activities at Other Sites** **in FY06-FY08**

In early FY06, the electro-polishing capabilities at JLab would be
commissioned using cavities provided by DESY. In addition, JLab would
upgrade its testing infrastructure to allow vertical testing of 1.3 GHz
cavities. JLab would also prepare to receive vertically tested cavities
from Industry/Cornell and dress, test, and ship them to Fermilab for
string assembly. It is possible that the KEK cavities would be dressed
at JLab and then shipped to Fermilab, the specifics are still under
discussion with KEK, JLab, and Cornell. Cornell would need to make minor
improvements to its infrastructure in order to test new cavities.

Argonne and Fermilab will complete a chemical processing facility for
the third-harmonic photo-injector cavities in FY05 and begin adaptation
for processing TESLA cavities. After that, the facility will be upgraded
to include electro-polishing.

4a. RF Power for the ILC Test Facility

The operating parameters and layout of the RF units for the ILC linacs
is in the process of being defined for both 500 GeV operations and a
future upgrade to 1 TeV operation. The choice of operating gradient is
tending towards 35 MV/m in both cases (to be compared to 23.4 MV/m in
the TESLA 500 GeV design and 35 MV/m in the TESLA 800 GeV design). The
power sources currently being developed can provide 10 MW of RF power so
it is natural to define an RF unit as the number of cavities powered by
such a source (i.e., one modulator and one klystron). Given the state of
cryomodule development and the desire to have some overhead in choosing
the ILC beam current, an ILC RF unit has been defined for test purposes
at SMTF as two cryomodules with eight TESLA-like (9 cell) cavities each.
Assuming 6% RF transport losses, each cavity in the RF unit could be
powered up to 530 kW with a 10% overhead. At 35 MV/m, a 15 mA beam could
be accelerated, which is about 15% more current than in the TESLA 800
GeV design. The present concept for the ILC cryomodule is based on the
TESLA Test Facility (TTF) design, which contains eight nine-cell
cavities. It may be cost effective for the ILC to have 12 nine-cell
cavities per cryomodule as was proposed in the TESLA Technical Design
Report.

In the past 24 cavities have been assumed for a TESLA high gradient RF
unit. This configuration is also possible at SMTF with three 8 cavity
modules and a beam current of 10 mA. Coupler power requirement and
injector beam requirements are consequently less. The specifications in
this proposal are based on a 10 mA beam and a ½% duty factor. These
requirements will be reviewed as ILC parameters evolve.

The power system at the facility will need to accommodate two complete
1.3 GHz RF units (each unit contains two eight-cavity cryomodules). Each
RF unit is nominally powered by one 10 MW klystron and modulator. These
klystrons will likely be purchased from one or more of the three vendors
(Thales, CPI and Toshiba) that DESY has contracted to develop such
tubes. These vendors have produced prototype 10 MW tubes but none has
yet performed at the level required for the SMTF. The development of
these tubes by DESY will undoubtly continues, especially as they will be
used for the DESY-based XFEL project as well. In the meantime, FNAL owns
commercial 5 MW tubes that could be used instead (one per cryomodule).
Specifically, they have a Thales 2104 klystron that is a spare for the
A0 injector and they recently acquired six Thales 2095 tubes that were
originally at LANL (5 were in operation there). It is anticipated that,
with coordination from the ILC-Americas collaboration, SLAC will lead
the ILC RF power source efforts, and source development and testing will
be carried out there as well.

Two modulators for SMTF are currently under construction at Fermilab.
These are designed specifically to power any of the following: the 10 MW
1.3 GHz multi-beam klystrons from Thales, CPI, or Toshiba; the 325 MHz
JPARC/Toshiba klystron planned for the β \< 1 linac, or the commercial
5 MW, 1.3 GHz klystrons. The modulators can be reconfigured to support
pulse widths of 1.5 msec for ILC and 3 msec or 4.5 msec for the Proton
Driver. A few types of klystrons and modulators will be needed for the
SMTF. We assume that modulators include pulse transformers when
necessary.

The proton driver would like to use a β = 1 cryomodule as a test bed for
the fast ferrite phase shifters used to provide individual phase and
amplitude control for individual cavities. These tests will take
advantage of the beam loading available at SMTF as well as the Lorentz
detuning from the high cavity gradients to perform a full system test.
The ferrite tuners are also of interest for ILC to minimize the RF and
cryogenic power dissipation.

The modulator and the klystron needed for the ILC test facility is
described below. The 5 MWatt and 10 MWatt multibeam klystron will be
acquired from industry. The modulators will be built by a collaboration
between SLAC and Fermilab with components acquired from industries. The
efficiency of the modulator is assumed to be about 67%. Therefore a 10
MW klystron requires a roughly 15 MW modulator. We plan to build two
types of modulators. The RF power requirements for the ILC modules at
each phase are:

-   Phase 1- one 15 MW modulator (B1), one 5 MW klystron

-   Phase 2- one 15 MW modulator (B1), one 10 MW klystron

-   Phase 3- two 15 MW modulators (one new B3), two 10 MW klystrons (one
    new)

A variety of different prototypes of both klystrons and modulators
should be fabricated and tested as part of the RF power development
program. Several klystrons and modulators exist or are in the process of
being fabrication in FY05. We will assume the following plan for the
proposed phases for cost and resource estimates for FY06 and beyond:

> Phase I

-   Complete fabrication of one 15 MW modulator (B1)

> Phase 2

-   Build one 15 MW modulator (development or B3)

-   Procure one 10 MW klystron & one spare

> Phase 3

-   Build one 15 MW modulator (B4)

In addition to modulators and klystrons, other klystron and RF ancillary
equipment is needed. This ancillary equipment includes:

-   Klystron auxiliaries ( shielding, solenoid, solenoid power supply,
    filament supply, vacuum pump power supply)

-   Waveguide, splitters, directional couplers, circulators, loads (This
    is the equipment that takes the RF power from the klystron to the
    input couplers of the cavity.)

-   RF system controls-interlocks

-   Low level RF system (LLRF) including Piezo

-   Fast Phase Shifter and its control

The LLRF controls-interlocks, and Fast Phase Shifters are all systems
that will be undergoing development so it is expected that more than the
minimum necessary will be developed, built and operated.

[ILC Test Facility RF Systems Table]{.underline}

# 

+--------+-------+-----------+---------+---------+---------+---------+
| System | Phase | Cavity    | K       | K       | Mo      | Mo      |
|        |       |           | lystron | lystron | dulator | dulator |
|        |       |           |         | status  |         | status  |
|        |       |           | nominal |         |         |         |
|        |       |           | power   |         |         |         |
+--------+-------+-----------+---------+---------+---------+---------+
| One    | 1,    | 8 cavity  | Thales  | exists  | 15 MW   | Under   |
| Module |       | module    |         | \\spare | "Big"   | fa      |
|        |       |           | TH2104C |         |         | b/parts |
|        |       |           |         |         |         | procure |
|        |       |           | 5 MW    |         |         |         |
+--------+-------+-----------+---------+---------+---------+---------+
| 2      | 2     | 2, 8      | 10      | New     | 15 MW   | New     |
| Cryo-  |       | cavity    | MWatts  |         | "Big"   |         |
| m      |       |           |         |         |         |         |
| odules |       | C         |         |         |         |         |
|        |       | ryomodule |         |         |         |         |
+--------+-------+-----------+---------+---------+---------+---------+
| 4      | 3     | 4, 8      | 10      | New     | 15 MW   | New     |
| Cryo-  |       | Cavity    | MWatts  |         | "Big"   |         |
|        |       |           |         |         |         |         |
| m      |       | C         |         |         |         |         |
| odules |       | ryomodule |         |         |         |         |
+--------+-------+-----------+---------+---------+---------+---------+
| spare  |       |           | Thales, | 6 units |         |         |
|        |       |           | T       |         |         |         |
|        |       |           | hompson | mod     |         |         |
|        |       |           |         | anode   |         |         |
|        |       |           | TH      |         |         |         |
|        |       |           | 2095A   |         |         |         |
|        |       |           |         |         |         |         |
|        |       |           | \~5 MW  |         |         |         |
+--------+-------+-----------+---------+---------+---------+---------+

4b. High Gradient SRF Cavity R&D

Improved understanding of gradient-limiting mechanisms, together with
technology advances through world-wide R&D are responsible for the
steady increases in performance in the last decade. Gradients of 35 - 40
MV/m at Q values of 10^10^ are now achieved in one-meter long
superconducting structures suitable for the 500 GeV International Linear
Collider.\
\
One goal of future R&D programs is to push gradients and Q values even
higher for TeV energies, gradient overhead, or cost savings. But above
40 MV/m the surface magnetic field approaches the fundamental limit at
which superconductivity breaks down.  One way to circumvent this limit
is to modify the cavity shape to reduce the ratio of the peak magnetic
field to accelerating field.

About two years ago, Cornell introduced a re-entrant shape which lowers
the surface magnetic field by 10%.   JLab has also introduced the Low
Loss (LL) shape with similar peak magnetic field reduction. Although
field emission is aggravated by the higher electric field, it does not
present a "brick wall" limit because of the success of high pressure
rinsing in eliminating field emitters.  The re-entrant shape has the
same beam aperture as the TESLA shape, which is important for
maintaining favorable beam-cavity interaction features.  The LL shape
has a smaller aperture.  HOM spectra studies as well as Lorentz force
detuning studies are in progress at FNAL on both shapes.\
\
 A 7-cell LL cavity at JLab reached Eacc =  39 MV/m at a Q value of
5x10^9^.   The first re-entrant single cell cavity fabricated at Cornell
reached a world record accelerating field of 46 MV/m at a Q value of
10^10^.  Both shapes are worthy of further exploration, as well as
development of other shapes.  .\
\
In phase I of the SMTF program, we propose to fabricate a 9-cell
re-entrant cavity.  KEK is planning to fabricate  9-cell LL cavities. A
comparison of the maximum gradients reached with these structures will
guide us to assess whether the basic TESLA design can be improved.  If
the result is positive, in Phase II we will fabricate four 9-cell
cavities and aim to put these in cryomodules.

4c. Accelerator Physics Studies for the β = 1 modules

The beam parameters listed below are the maximum values desired at SMTF
based on the possible ILC operating parameters (although a beam current
as high as 15 mA would allow operation similar to that in the TESLA 800
GeV design, only 10 mA may be possible with the present injector). These
parameters would serve as guidelines when considering radiation
shielding, beam dumps, cryogenic cooling and RF power. Operation with
ILC-like parameters is demanding with respect to radiation shielding and
cryogenic cooling, and if necessary, the initial pulse rate may be
lowered by a factor of 10 or more to ease the requirements. These
parameters may change as ILC design progresses.

  ------------------------------------- --------------- -----------------
  RF Pulse Length                       msec            1.5

  Pulse Rate                            Hz              5

  Beam Pulse Length                     msec            1.0

  Beam Current                          mA              15

  Electrons per Bunch                                   2e10

  Bunch Spacing                         ns              337
  ------------------------------------- --------------- -----------------

To study basic cavity performance during beam operation, the injector at
SMTF should provide bunch trains comparable to those expected in the
ILC. Addition requirements in this regard are:

-   Bunch Charge: up to 2e10 electrons

-   Bunch Length: as low as 300 microns rms (typically 1 mm RMS).

-   Bunch Spacing: nominally 337 ns with option of halving this.

-   Bunch Energy Stability: \< 1% rms average

-   Current Stability: \< 5% rms, (preferably less).

-   Number of Bunches: up to 2820.

-   Pulse rep rate = up to 5 Hz

**Experimental Program**

Outlined below are some of the ILC studies envisioned at SMTF, many of
which require beam capability.

-   Determine the maximum operating gradient of each cavity and its
    limitations.

-   Evaluate the gradient spread among cavities and its operational
    implications.

-   Measure dark currents, cryogenic load, dark current propagation, and
    radiation levels.

-   Measure alignment of the quadrupole, cavities and BPM in-situ using
    conventional techniques (e.g., wire or optical systems).

-   Measure vibration spectra of the cryomodule components, especially
    the quadrupole magnet.

-   Measure system trip rates and recovery times to assess availability.

-   Develop LLRF exception handling software to automate operation and
    reduce downtime.

-   Evaluate failures with long recovery times: vacuum, tuners, piezo
    controllers, and couplers.

-   Measure beam energy to provide an independent and accurate
    measurement of the accelerator gradient (rf based techniques are not
    as accurate).

-   Characterize long-range wake-field by measuring frequency spectra of
    bunch positions downstream of the cryomodule. Search for high Q
    cavity dipole modes that could cause beam break-up in the ILC.

-   Demonstrate that a \< 0.1% bunch-to-bunch energy spread can be
    achieved in a 1 msec long bunch train.

-   Measure the beam kicks caused by the fundamental mode fields to
    determine the impact on transverse beam motion in the ILC.

Assess ability to center the beam based on the HOM dipole signals.

5\. Proton Drive Test Facility

The Proton Driver is an 8 GeV proton linac. The last 85% of the linac (1
GeV to 8 GeV) is comprised of β=1 TESLA modules and will benefit from
the ILC program. The synergy between ILC R&D and Proton Driver is
further reinforced by the almost complete overlap of an ILC module test
bed and what will be needed for many aspects of Proton Driver R&D. The
proton driver will need 288 TESLA cavities in 36 cryomodules, as well as
96 low beta elliptical cavities in 12 cryomodules, all at 1.3 GHz. Two
main uses are foreseen for the β\< 1 test area: pulsed-mode front end
linac for the Proton Driver, and a possible production test facility for
RIA cavities and cryomodules.

The initial RF systems will support pulsed mode operation at 325 MHz
(one quarter of the ILC's 1300 MHz) and extend the TESLA-style RF fan
out from one large Klystron to a large number of cavities. This will
support development of a family of "ILC-compatible" β\<1 superconducting
cavities to be developed by members of the SMTF collaboration. These
include single, double, and potentially triple spoke SRF cavity
resonators. At higher beta, the Proton Driver will also use cryomodules
with 1300 MHz elliptical cavities that will be tested in the 1300 MHz
test area.

![](media/image4.wmf){width="6.163194444444445in"
height="4.024305555555555in"}

Fig. 5.1 - Beta \<1 test area. The entire front-end linac is driven by a
single 325 MHz klystron. Although the single klystron should be capable
of driving the entire front end linac up to energy of \~100 MeV, the
beam energy will be limited to \~30 MeV by the length of beam line
enclosure available.

**Beam Tests.** A second phase of operation would add an H- source, and
RFQ, and Medium Energy Beam Transport (MEBT) operating from the same
pulsed Klystron that operates the SRF cryomodules. This would provide a
beam-based test bed for LLRF and resonance control when driving low-beta
ion beams with multiple cavities driven from a single Klystron.
Emittance measurements, chopping, and laser stripping experiments will
be possible.

![](media/image5.wmf){width="6.127083333333333in"
height="4.385416666666667in"}

Fig. 5.2 -- Evolution of technology to be tested in SMTF beta\< 1 linac.
The beta\<1 test area would support a 325 MHz front end linac pattered
on the JHF/JPARC front end, then use SRF spoke resonators patterned on
the RIA cavities. The 1300 MHz test area would support beta\<1
elliptical cavities and cryomodules, as well as beta=1 section patterned
on the ILC main linac.

A key new technology is the demonstration of fast high-power phase
shifters for SRF resonance control of individual cavities while driving
a large number of cavities from a single large Klystron.

5a. 325 MHz Pulsed RF Systems for β\<1 Test Area

A single 3MW Klystron (the Toshiba E740A currently in production for
JPARC) will provide pulsed RF power for the 325 MHz beta\<1 linac. See
fig.5.

The RF systems would be designed to support both the initial and upgrade
beam pulse parameters for the Proton Driver. Initial operation would
support beam pulses of (8.3 mA x 3 msec x 2.5 Hz), with an upgrade
scenario requiring (25 mA x 1 msec x 10 Hz). Two modulators are
currently under construction which can be reconfigured to support either
of these pulse parameters.

![](media/image6.wmf){width="5.740972222222222in"
height="3.5395833333333333in"}

Fig. 5.3 - The RF distribution system for the 325 MHz beta\<1 pulsed SRF
linac. In a TESLA-like scheme, directional couplers are used to split
off power for each cavity from a long waveguide running parallel to the
linac. Individual resonance control for each cavity is provided by fast
tuners using magnetically biased YIG ferrite to provide individual phase
and amplitude control for each cavity.

5b. Program sequence for the 325 MHz Pulsed Linac β\<1 Test Area

1)  Modulator construction (already underway).

2)  Order the 325 MHz Klystron, for delivery in FY06

3)  In parallel, construct and begin cold tests of the RF fan out
    waveguide and directional coupler, to understand cross talk between
    couplers and related issues.

4)  Continue development of the fast-ferrite tuner modules, with the
    goal of having functional prototypes at each required power level by
    the end of FY05.

5)  Begin prototyping of 325 MHz cavities in various beta ranges by
    members of the SMTF collaboration.

6)  Funds permitting begin procurement of the H-/RFQ front end.

7)  Continued development and simulation of LLRF hardware and control
    algorithms using the ferrite tuners.

8)  Integrated system test of the front-end linac, 325 MHz Klystron, RF
    distribution, ferrite tuners and LLRF control.

6\. CW Test Facility

Superconducting RF structures operated in cw mode have advantages in
providing high gradients, extremely stable RF fields, inherently small
perturbative effects on the beam, and with RF power requirements
considerably less than equivalent normal conducting structures. Taking
advantage of advances made in superconducting RF technology in recent
years, several proposals have been developed for a variety of
applications of cw scrf, including an upgrade to the existing CEBAF
linacs, the Rare Isotope Accelerator (RIA) (discussed in the β\< 1
section), storage-ring synchrotron radiation sources, free electron
lasers, energy recovery linacs (ERL's), recirculating linacs, and beam
conditioning devices such as harmonic cavities for manipulation of
longitudinal phase space, and transverse deflecting cavities.

The high quality factor of superconducting structures (monopole mode
Q~0~ \~ 10^10^) results in a very long filling time of 2.4 s for
unloaded 1.3 GHz structures, and very small intrinsic bandwidth (≈ Hz)
for stable operation. Overcoupling the cavity to the RF power input port
reduces the quality factor to a low external Q (Qext) and decreases the
filling time, but requires additional RF power to overcome reflections
introduced at the coupler. In some applications the beam loading
requirements provide a strong reason to lower the Q of the cavity
resonance such that input conditions closer approximate a match to the
beam loading. But for many applications where the system is not heavily
beam loaded, significant overcoupling has a direct consequence in
increased RF power costs. In such cases then, the coupling and the
filling time are limited primarily by the ability to provide feedback of
the system against field fluctuations induced by microphonics. For
example, a 50 Hz cavity/feed system bandwidth results in an external
quality factor Q~ext~ of 2.6x10^7^ for 1.3 GHz cavities, and the cavity
filling time is then several milliseconds. Typically, power is applied
to pulsed standing wave cavities for about three time constants before
the beam enters the structure, to allow time for energy to build up in
the cavity so that the required field can be developed. The applications
of interest discussed here require bunch rates significantly exceeding
the capabilities of a system with 1-10 ms time constant, and the
superconducting linac must be operated in continuous wave (cw) mode. The
resultant power dissipation due to RF currents on the cavity inner
surfaces increases significantly over the pulsed design parameters, for
example a TESLA accelerating cavity operating at 20 MV/m cw dissipates
approximately 40 W at liquid helium temperature, compared with \~ 1 W
for the nominal pulsed operating mode (at about 1% duty factor).
Operating in cw mode at a gradient of up to 20 MV/m, or with equivalent
surface currents in deflecting (dipole mode) cavities, requires
development and testing of systems to accommodate the large thermal
load.

Application of cw SRF in facilities such as listed above drives advances
in a broad range of accelerator communities, including storage-ring
synchrotron light facilities, free-electron lasers (FELs), electron-ion
colliders, and nuclear physics facilities. Dedicated research and
development in cw superconducting structures offers significant
potential improvements and capabilities for these facilities and opens
up new possibilities for the science performed with these instruments.

Several RF structures are being developed for cw applications, at
different frequencies and with different parameters, but with similar
and some key overlapping issues to be addressed. A number of facilities
are currently operational and active in research and development of cw
SRF for application in specific projects for light sources and nuclear
physics facilities, and a number are in the proposal stage. Existing
experimental capabilities include facilities at Cornell, BNL, and TJNAF
JLab. R&D interests in application of cw SRF include:

-   Demonstrate high gradients in TM~010~ mode cw operations \~ 20 MV/m

-   Demonstrate high transverse deflecting fields \~ 5 MV/m in TM~110~
    mode (5 MV transverse kick for 1 m of RF structure)

-   Demonstrate high Q values in cw operations. One goal, for the
    TM~010~ mode, is Q~o~ \> 3x10^10^

-   Demonstrate high external Q values at operating gradients of \~20
    MV/m, with a goal of Q~ext~ \> 1x10^7^ for the TM~010~ mode in low
    beam loading applications

-   Demonstrate high stability and control of microphonics, with a goal
    of phase error \< 0.1° and amplitude error \<10^-4^

-   Demonstrate wakefield suppression and stable operations with
    realistic beam parameters (strongly dependent on application)

6a. Applications for cw SRF in accelerator-based facilities

Recirculating linacs and ERLs, driven by cw SRF linacs, are proposed
accelerator-based x-ray sources that allow high peak and average
brilliance, high temporal and spatial coherence, and ultra short light
pulses covering wavelengths from infra-red to x-rays, depending on the
beam energy. Using stable beams from a cw SRF linac allows utilization
of the very low 6-dimensional electron beam emittance produced in
high-brightness electron sources -- a significant advantage over storage
ring beam quality which is limited by stochastic effects (quantum
emission, intra-beam scattering, radiation damping).

ERLs also allow high average photon flux by using very high beam power
(high bunch rate) and recovering the beam energy. Energy recovery is
achieved by passing the electron beam, following acceleration and x-ray
production, back into the linac in the opposite phase to the accelerated
beam. The energy in the electron beam is deposited into the SRF
cavities, building field for acceleration of fresh beam from the
electron source, and providing enormous savings in electrical power.
There have been several demonstrations of the ERL technique, most
recently at JLab up to 1100 kW average beam power has been recovered in
an ERL by recirculating 7.5 mA of beam current at 145 MeV, and up to 9
mA average beam current has been recirculated at 88 MeV. The principle
of energy recovery has also been demonstrated at higher energy at CEBAF,
where 80 μA of cw beam current was accelerated from 20 MeV to 1 GeV, and
then stably decelerated back to the injection energy with full energy
recovery.

JLab's 12 GeV CEBAF Upgrade project has produced high gradient (20-25
MV/m), high Q~0~ (\> 8x10^9^) cw SRF accelerating structures. Tight
control and mitigation of microphonics noise remains to be demonstrated.

LBNL and MIT are developing accelerator concepts based on proposed
developments of the TESLA technology into the cw operating mode. These
facilities are designed for high peak x-ray flux and brightness from
FELs using high-quality electron beams accelerated in cw SRF linacs,
either recirculating or single-pass.

ANL is conducting a study for future upgrades for the APS storage ring
that could include a full energy linac injector followed by an XFEL
(Lew, 2002), or an ERL injector (Cho, 2003), both of which benefit from
cw SRF R&D for accelerating structures. Either option could provide
order of magnitude brightness improvement through short bunches and
either CW injection or high injection rates into an ultralow emittance
ring (very low lifetime) (Eme, 2001).

Cornell and TJNAF JLab are developing light sources based on x-ray
production by spontaneous emission in insertion devices with high
coherence achievable from high-brightness electron beams, and using an
ERL to achieve high average power. Cornell for example is conducting a
study towards a 100 mA, 5 GeV beam with the equivalent of 500 MW of
power. At BNL a high-current ERL for electron cooling of the RHIC beams
is under construction, with the aim providing of Ampere-scale beams
using a superconducting linac. The facility will be operational in 2007,
and will include the following:

> 1\. SRF photoinjector providing 1.5 nC bunches at a repetition
> frequency up to 350 MHz.
>
> 2\. 1 MW CW klystron at 703.75 MHz for driving the gun.
>
> 3\. 5-cell linac cavity at 703.75 MHz, designed for ultra-high current
> (up to ampere level CW) with full damping of HOMs and a loss factor
> six times smaller than TESLA 1.3 GHz cavity.
>
> 4\. 50 kW IOT transmitter for the linac cavity.
>
> 5\. Energy recovery loop for ERL operation.
>
> 6\. All infrastructures as necessary.

This facility will pursue all the SMTF goals for CW SRF at the frequency
of 703.75 MHz with a performance extended to high-current machines. At
BNL a high-current ERL for electron cooling of the RHIC beams is under
development, with the aim providing of Ampere-scale beams using a
superconducting linac.

ANL and LBNL are developing proposals for ultra fast x-ray production in
conventional storage rings, using cw SRF cavities. In this scheme, the
electron bunches receive a head-tail kick in a cw SRF dipole mode
(TM~110~) deflecting cavity, phased such that the beam centroid passes
through the cavity at zero phase and receives no perturbation, while the
head and tail receive transverse kicks in opposite directions. In a
downstream radiating magnet or insertion device, the time-correlated
transverse kick results in an angular or spatial distribution of the
radiation emitted by electrons along the length of the bunch. The
resulting extended x-ray pulse with correlated distribution may be
imaged by asymmetrically-cut crystals or aberration-corrected x-ray
optics, to result in an x-ray pulse of approximately picosecond
duration. After the bunch radiates, the kick introduced is cancelled by
a downstream deflecting cavity. High repetition rates, in principle as
high as 500 MHz (ALS bunch rate), may be achievable using this
technique, providing an ultra fast x-ray source with characteristics
suitable for a variety of time-resolved photoemission and magnetism
experiments. Several challenges have emerged in the ANL study, including
cavity design and development of adequate cw power sources for high
frequencies (S-band) and RF phase stability (Bor, 2005).

For a different application, SRF deflecting cavities have also been
under development for the high luminosity colliders at Cornell, KEK, and
SLAC, and are often referred to as "crab" cavities. Also, Fermilab has
developed a SRF crab cavity for rf-separated Kaon beams. Engineering
design and prototype tests were carried out for a 3.9 GHz, 5 MV/m,
13-cell design. A single-cell prototype achieved Q~0~ 1e9 up to 10 MV/m.
Work continues on a 5-cell prototype to meet the requirement. (Cham,
2001). ANL and LBNL are developing proposals for ultrafast x-ray
production in conventional storage rings, using cw SRF cavities. In this
scheme, the electron bunches receive a head-tail kick in a cw SRF dipole
mode (TM~110~) deflecting cavity, phased such that the beam centroid
passes through the cavity at zero phase and receives no perturbation,
while the head and tail receive transverse kicks in opposite directions.
The scheme has For a different application, SRF deflecting cavities have
also been under development for the high luminosity colliers at SLAC,
Cornell, and KEK, and SLAC, and are often referred to as a "crab"
cavities. y, phased such that the beam centroid passes through the
cavity at zero phase and receives no perturbation, while the head and
tail receive transverse kicks in opposite directions. In a downstream
radiating magnet or insertion device, the time-correlated transverse
kick results in an angular or spatial distribution of the radiation
emitted by electrons along the length of the bunch. The resulting
extended x-ray pulse with correlated distribution may be imaged by
asymmetrically-cut crystals or aberration-corrected x-ray optics, to
result in an x-ray pulse of approximately picosecond duration. After the
bunch radiates, the kick introduced is cancelled by a downstream
deflecting cavity. High repetition rates, in principle as high as 500
MHz (ALS bunch rate), may be achievable using this technique, providing
an ultrafast x-ray source with characteristics suitable for a variety of
time-resolved photoemission and magnetism experiments. Several
challenges have emerged in the ANL study, including cavity design and
development of adequate cw power sources for high frequencies (S-band)
and RF phase stability (Bor, 2005).

6b. Goals for a cw SRF test facility at SMTF

Existing R&D facilities are already addressing many of the outstanding
and pressing questions in application of cw SRF in particle
accelerators, particularly for accelerating structures. In this proposal
the SMTF would provide for experimental study of aspects of both
accelerating and deflecting cavity structures and cryomodule performance
not specifically addressed by other programs. The SMTF goals may be
specifically identified as demonstration of the following:

-   High Q values in cw operations of accelerating cavities at 20 MV/m,
    goal of Q~o~ \> 3x10^10^

-   High Q values in cw operations of deflecting cavities at transverse
    kick voltage of 5 MV/m, goal of Q~o~ \> 5x10^9^

-   High stability and control of accelerating fields, goals of phase
    error \< 0.01° and amplitude error \<10^-4^

-   The above performance in the presence of electron beam of 1 nC
    charge

This proposal presents a program of experimental investigation of cw SRF
not addressed at other facilities within the US.

The first tests at SMTF can also address some of the following important
issues:

-   Thermal management for a range of projected Q values

-   HOM (higher-order modes) and LOM (lower-order modes) damping
    validation

-   Cavity tuning control

-   Power coupler designs

Equipment will be required to allow determination of cavity Q values,
gradient, stability, HOM and LOM characteristics, thermal load at a
variety of locations within the cryomodule, input power, dark current,
etc.

In addition, couplers and tuners and other cryomodule components would
be fabricated to extend the full range of expertise and technology
required for the major projects envisioned. For both deflecting cavities
and for accelerating cavities, strong damping of HOM's through specially
design couplers is required, and for the deflecting TM~110~ mode
cavities, there is an additional challenge of damping the lower
frequency TM~010~ mode which is expected to have a large impedance and
damping the other polarization of the deflecting mode.

Capabilities of the SMTF to facilitate operation of a cw test stand
would include ability to explore high gradient cw performance along with
Q and dark current measurements without beam. Tuner tests, HOM
measurements, and cavity microphonic tuning feedback systems test with
the cryomodule would be performed to establish the necessary
specifications.

Average beam power requirements for the cw cavity investigations are
modest, 1 nC bunch current at as high a repetition rate as possible, and
would require an RF photocathode source. Synchronization of the cavity
phase to the beam will be required to accurately time the arrival of a
bunch in the cavity, and measure the head-tail kick of the beam after
passing through the deflecting cavity cryomodule.

The above goals encompass research and development topics critical for
the development of cw operation for many proposed applications. For
example, the exacting phase and amplitude goals require development of
low-level RF systems which would have benefits in many SRF applications.
The cryomodule tested at SMTF may be subsequently tested at higher beam
currents at Jllab, at BNL or at Cornell.

The cryomodule and cavities may be constructed in US industry, and
processed and tested using existing infrastructure at US labs.

The provision for a cw test area in the SMTF would allow R&D into cw SRF
cryomodules for accelerating structures and deflecting cavities,
required by future linacs, recirculating linac's, high current storage
rings, and ERL's. The SMTF would provide a location and infrastructure
for development of cw SRF systems to meet these needs and for other
future developments, and would be complementary to the existing
facilities and R&D programs. Strong intellectual and technical
interactions between cw, RIA, PD, and ILC enthusiasts (many of whom are
the same people) would be of benefit to all communities.

## 6c. Prototype cw cryomodules for SMTF

We propose two projects for development of cw SRF at SMTF, the first is
aimed at improving performance of accelerating cavities and the second
at developing deflecting cavities.

For accelerating cavity development in cw applications, the multi-cell
cavity for the ILC, at 1.3 GHz, offers an existing design having
parameters suitable to application in cw mode to meet the needs of
future facilities with modest beam loading (\~ 10 µA). To take advantage
of developments to date in SCRF, use of the cavity design developed for
ILC would provide a suitable prototype to address the performance
questions listed above for cw operations. These particular questions are
not being addressed at 1.3 GHz at other facilities (BNL is addressing
the high-current ERL at 0.704 GHz).

R&D into deflecting cavity design would focus on single-cell cavities
operating at the third or fourth S-band, which is anywhere between the
3rd-10th harmonic of typical storage ring RF system. These could provide
a deflecting kick of hundreds of kV to MV. The cavities may be used in a
cryomodule to providing a transverse kick that may typically be required
for storage ring ultrafast x-ray production applications. Operating in
the TM~110~ mode, the deflecting cavities are deformed by flattening
opposite sides (squashing the cavity), such that the two dipole mode
polarizations are split in frequency and in spatial orientation. The
cavity would be mounted in the accelerator with the desired orientation
of the transverse kick axis. The critical design parameters for
deflecting cavities are the transverse shunt impedance and the peak
surface magnetic field. For the TESLA accelerating cavities, the maximum
surface magnetic field is approximately 0.1 T at 25 MV/m, with a
theoretical limit about twice that. The cavity gradient is limited by
magnetic field quenches, and also by field emission. Careful design will
be required to minimize multipacting, and test at the SMTF will be
essential to qualify cavities for installation in operating light source
user facilities.

We propose to design and build a two-cavity cryomodule for tests of
deflecting cavities at the SMTF, for application in storage ring
ultrafast x-ray production techniques. Installing two cavities in a
cryomodule allows experimentation with adjusting thermal loads, study of
HOM and LOM dampers, as well as study of potential "cross-talk" between
cavities and components adjacent to each other. The cavities would be
designed to operate at a nominal 2K, with possibility of lower
temperature tests.

For research and development of high gradient, high quality factor cw
accelerating structures, we propose to also build a two-cavity
cryomodule. The design would incorporate two of the ILC-like multi-cell
cavities mentioned above, into a single cryomodule, distinct from the
deflecting cavity cryomodule. Existing designs such as the cryomodule
built for the Rossendorf facility may be developed by US industry and
institutions for this application.

Thermal management

The dynamic heat load in the cw SRF cavities is inversely proportional
to the cavity unloaded Q value, Q~0~. Typical Q~0~ values for L-band
dipole TM~110~ mode cavities are \~ few 10^9^, and an order of magnitude
greater for monopole TM~010~ mode cavities. Development of high Q
cavities has significant advantages to cw operations, in reducing RF
power requirements. We note that development of Q~0~ \> 3x10^10^ for the
accelerating monopole mode is particularly important for larger,
multi-GeV, linacs, and Q~0~ approaching 10^10^ will enhance deflecting
cavity operations.

Lowering the temperature to 1.8 K increases the theoretical Q reachable.
Excellent magnetic shielding will be necessary to screen the earth's
field down to about one mGauss. (The earth's field flux quanta get
trapped in the niobium walls, due to the presence of imperfections,
impurities and oxides, thereby limiting the Q-value).

Operating at 1.8 K to reduce the BCS resistance and increase the
theoretical maximum Q-value will demand larger pumps to reach the lower
helium vapor pressure corresponding to 1.8 K. Even though the goal is to
reach a Q of 3x10^10^ for the TM~010~ mode, and in excess of 5x10^9^ for
the TM~110~ mode, a cw SMTF module should be equipped with features to
handle Q values down to a factor three to five lower, so that we may
learn how to deal with high heat loads, if the high Q's aimed for are
not realized, or partially realized. The Meson cryogenic plant will be
able to provide 1.8 K at a reduced capacity.

A TM~010~ mode cavity operating in cw mode at 20 MV/m with a Q~o~ of
1x10^10^ may be expected to generate approximately 40 W heat load at 2 K
as a result of RF current flow on the inner surfaces of the cavity.
Added to this is approximately 8 W heat entering the cavity niobium body
from the input RF power coupler. A 1.5 GHz TM~110~ cavity operating in
cw mode at transverse kick 5 MV/m with a Q~o~ of 2x10^9^ may be expected
to generate approximately 10 W heat load at 2 K as a result of RF
current flow on the inner surfaces of the cavity. Added to this is
possibly 10 W heat entering the cavity niobium body from the input RF
power coupler (assuming a coaxial coupler designed to damp the HOMs and
LOM). Theseis dynamic heat loads are is to be transferred through the
niobium to the cavity outer surface in the super-fluid helium liquid
bath, then to the super-fluid helium surface where boiling occurs at 1.8
K, without quenching the cavity. In a super-fluid helium test bath there
is no problem transferring this heat from the cavity outer surface to
the super-fluid helium surface, however, the transport of about 50 W
from the cavity outer surface through the helium tank, the feed-pipe and
the header-pipe requires careful engineering.

In order to provide sufficient heat transfer from the cavity outer
surface to the surface of the liquid in the header, the following
cryogenic module design issues are to be addressed:

-   The number of feed pipes between the RF cavity helium tank and the
    two-phase helium stand pipe

-   The location of the helium feeds on the helium tank

-   The inside diameter of the helium tank relative to the cavity outer
    diameter, to control the spacing between the cavity convolutions and
    the cavity helium tank inner wall through which heat must flow

-   The diameter of the liquid helium feed pipes from the stand-pipe to
    the tank

-   The diameter of the two-phase helium header pipe

A 1.5 GHz dipole mode cavity operating in cw mode at transverse kick 5
MV/m with a Q~o~ of 2x10^9^ may be expected to generate approximately 10
W heat load at 2 K as a result of RF current flow on the inner surfaces
of the cavity. Added to this is possibly 10 W heat entering the cavity
niobium body from the input RF power coupler (assuming a coaxial coupler
designed to damp the HOMs and LOM).

Lower frequencies also reduce the BCS resistance of a cavity, and other
laboratories are pursuing designs based on lower frequencies. This work
would be complementary to SMTF.

Control of cavity HOM's and wakefields

For high average power operations, cavity Higher Order Modes (HOMs) may
present significant problems due to the perturbative effects of the
wakefields persisting from one electron bunch to the next.

In the case of a dipole mode cavity, there also exists a lower frequency
monopole mode, which typically has a large shunt impedance, so in this
case we must also address the Lower Order Modes (LOMs). Damping of the
LOM without significant coupling to the deflecting mode presents a
particular challenge that this program would address. The unwanted
dipole mode polarization must also be dealt with -- either by tuning its
frequency out of harms way, or by selective damping.

Since the SRF cavities require very smooth boundaries and transitions,
HOM/LOM damping devices are located at the ends of the cavities, in the
beam pipe, and may be in a cold section of the cryomodule or external in
a warm section.

Effective HOM/LOM damping is required to reduce resonant beam impedance,
raise coupled-bunch instability thresholds, and allow stable operations.

Although the majority of these tests can be meaningfully conducted at
high average current facilities, beam tests planned with the SMTF beam
would help validate bench measurements of modes and Qs. These results
would be useful input to beam stability assessment for various
applications at higher currents.

Feedback control of cavity tuning variations

A significant problem for the use of superconducting cavities is the
fact that systematic as well as random tuning errors are orders of
magnitude larger than the intrinsic bandwidth. An example for the
systematic part is the detuning by the radiation pressure forces or
Lorentz force detuning, which may be as large as 360 Hz for TESLA
cavities at a gradient of 20 MV/m. While this is of great concern for
pulsed cavities, it can be easily corrected in the cw application where
the field is continuous.

More serious are the random tuning deviations. The random tuning
perturbations fall in two categories:

A.  [Relatively slow perturbations]{.underline}, with periodic intervals
    in the minute range. Random variations of the helium pressure
    represent a common cause.

B.  [Fast perturbations]{.underline} due to microphonics in the acoustic
    frequency range, caused by local mechanical stimuli (pumps,
    turbulence in the helium flow etc). The response is shaped by
    structural resonances and directional sensitivities of the cavities.

Slow mechanical tuners may be used to eliminate the slow perturbations.
Faster feedback systems are required to control the effects of
microphonics, which may extend their influence to approximately ± 25 Hz
from the RF frequency. To control against such rapid tuning variations,
the RF system must provide sufficient generator power to establish the
nominal field in the cavity under worst-case conditions of full detuning
by microphonics.

In addition, the impact of beam loading from a \~1 nC charge needs to be
investigated. Such a bunch would shock-excite the cavities and introduce
transient behavior of the RF fields that must be corrected by feedback
systems.

To achieve the maximum possible phase and amplitude performance from
these CW SRF systems high gains will be required in the controller
feedback loop. Adaptive feed-forward controllers will also be extremely
useful for the optimal suppression of periodic perturbations including
"microphonic" mechanical vibrations and beam loading. Many labs are
working on the development of these controller architectures including
LBNL, Cornell, TESLA, JLab JLab and MIT.

The requirement to maintain field in the cavities under the influence of
microphonics and beam loading has strong impact on the cavity RF
feedback system and RF power requirements, and thus costs. Techniques to
minimize detuning from microphonics may have significant impact in cw
SRF systems design. Beam loading from orbit offsets in deflecting
cavities can be significant and must be controlled or compensated; this
also potentially strongly impacts the RF power requirement.

While RF control tests with Q~ext~ \> 10^7^ and up to 10^8^ are
presently conducted at the Jefferson Lab FEL without and with beam,
demonstration of the more stringent phase stability requirement of 0.01
degrees is likely to await the SMTF.

To achieve the precision phase stability of 0.01 degrees the SMTF must
deliver a master RF timing distribution system with such accuracy or
better. The reference "clock: must perform as well as or better than the
device to be regulated. New RF synchronization designs which make use of
short pulse laser systems offer the potential to meet these
requirements. The ILC component of the SMTF should demonstrate Master
Oscillator and RF distribution systems which maintain a precision of 1
degree when projected to ILC length scales of 30 km. This requirement is
similar to the 0.01 degree goal for the CW section of the SMTF which
will have a length scale between 10-100 m.

Power couplers

Superconducting RF systems require very little power to generate large
accelerating gradients -- for example the TESLA cavities may develop 20
MV/m with only 40 W input power under ideal conditions. In order to
accommodate for tuning variations as discussed above, however,
significantly larger RF drive power is required at the lower external Q,
typically tens of kW per cavity for Qext ≈ 10^7^.

For dipole mode operation, there may be need to accommodate beam offset
from the mode axis, in which case the beam experiences the longitudinal
field of the dipole mode, and also deposits power into the cavity.
Additional drive power may be required to compensate for this beam
loading in high-current applications, but is not expected to be a
necessity in tests at SMTF.

Power couplers must transport this 10's kW power from warm waveguide or
coaxial supply lines, through intermediate temperatures, thermally
isolating sections, vacuum windows, to liquid helium temperature
components, and have mechanically adjustable components, while avoiding
multipacting and excessive heating. Choice of coaxial or radial coupling
arrangements will be made in the design stage.

## RF Transmitters

As described above, the intrinsic power demand for an SRF cavity
operating at 20 MV/m, Q~0~ = 10^10^ and 100 μA beam current is only 2040
Watts. The remainder of the power from a 10 kW power source is reflected
from the cavity structure and absorbed in an external load. This
additional power is required to maintain adequate control of the cavity
fields. Innovative transmitter designs including low insertion loss
external reactive tuners offer the potential to reduce the power demand
by factors of two or more. These reactive tuners are also the same
devices that could be used for individual cavity control in the ILC
configuration where a large 10 MW klystron feeds 32 cavities through a
waveguide distribution system. Successful testing of these efficient
amplifier systems at SMTF will benefit many existing and proposed
accelerator facilities.

Compensation of beam loading and microphonics in deflecting cavity
applications may require several 10s of kW cw RF power. Commercially
available cw RF power transmitters in the S-band, above 2.6 GHz in
particular, are not adequate. Although the specific RF frequency is to
be determined by the application, through this SMTF initiative it is of
benefit to the accelerator community to develop cw RF power transmitters
over a range of RF frequencies and power levels using a modular
approach.

## 6d. Infrastructure requirements for a cw SRF test facility

The SMTF should provide capability for measurements of cw SRF
cryomodules, with the installation of RF power, cryogenic fluids and
transport, and test beams of electrons.

The accelerating TM~010~ cavity tests will require, for each cavity, a
1.3 GHz klystron (or IOT) with approximately 15 KW of power to establish
20 MV/m operating field with control margin for dealing with
microphonics at the optimum external Q value, estimated to be about
2x10^7^. A high voltage power supply and a small amplifier are needed to
supply the klystron. We envision testing cryomodules initially with two
cavities per cryomodule.

For deflecting cavities, the operating frequency depends on the
application. Funding for the RF power components for this application
would be provided from the project source, and it is expected that the
systems would be removed for operation at the host institution following
tests at SMTF. The SMTF should reserve space in the cw area to
accommodate additional RF power requirements such as this.

The more demanding possibility of testing cw accelerating cavities at cw
at 20 MV/m with Q of 1x10^10^ would require 60 W/m at 2 K allowing for a
safety factor of 1.5. Assuming advances in technology would triple the
obtainable Q value, the cw cryomodule refrigerator would be sized for 20
W/m at 1.8 K and about 5 W/m at 4.5 K. However, to ensure capabilities
in early design stages, where the higher Q~o~ values may not be
initially obtained, the cryogenics plant should be designed with
capacity of 120 W at 2 K, allowing two accelerating cavities to operate
with a 50% design margin on cooling capacity.

Electron beam availability is highly desirable for measurement of cavity
performance under transient effects induced by bunches of 1 nC. Cavity
voltage and phase, and wakefields in the complicated electrodynamic
environment of cavities assembled in a cryomodule would be essential in
gaining confidence for employing cw SRF in demanding light-source
applications. Bunch lengths of 1 -- 10 ps, and transverse emittance of
order mm-mrad would be of interest. The proposed integration of the FNPL
facility into SMTF would provide beams useful for testing cw cavities.
Alternatively, a DC photoinjector could provide low current beams at MHz
repetition rates allowing precision measurements of the cavity fields
with a higher bandwidth probe.

In addition to RF power and cryogenics, the cw facility would require
technical support from the SMTF. To build the RF systems at SMTF would
require 1 FTE electrical engineer, 1.5 FTE electrical technicians, 1 FTE
mechanical technician. To support the installation, test, and operations
of two cryomodules proposed would require from SMTF approximately 0.5
FTE cryogenics engineer, 1 FTE mechanical technician, 0.5 FTE
controls/electrical technician, o.5 FTE vacuum technician.

The CW component of the SMTF will also have significant availability
requirements. For the facility to be effective in its research goals
operation must be available in excess of 3 months per year with
operational duration of at least two weeks and availability in every
three month calendar interval.

## Institutional and industrial involvement in the cw program at SMTF

Several institutions have been mentioned as having interests in cw scrf,
and some have experimental programs independent and complementary to
SMTF. For the two programs proposed here, we envision a collaboration of
institutions interested in light source development, and industry with
capabilities and interests in superconducting RF structure fabrication,
and cryomodule fabrication.

The institutional involvement will likely include Lawrence Berkeley
National Laboratory, Cornell University, Thomas Jefferson Laboratory,
Massachusetts Institute of Technology Bates Linear Accelerator Center,
Argonne National Laboratory, Brookhaven National Laboratory, and
Stanford Synchrotron Radiation Laboratory.

JLab in particular currently represents a major fraction of DoE\'s
existing investment in SRF technology. As a result of this investment
the capability exists for producing and delivering accelerating
structures and components from concepts to prototypes. With the existing
LLRF and high power capabilities, JLab is in a position to deliver an
entire vertical slice of a cw SRF module for testing at SMTF or JLab, as
appropriate.

## Relationship to International activities

Several institutions worldwide outside the US are active in research and
development of cw scrf, and several proposals for applications in
accelerators are being pursued. We note here the ELBE facility at
Rossendorf, Germany, the 4GLS project at Daresbury, England, and the
BESSY FEL proposal from Berlin, Germany.

At the ELBE radiation source in Rossendorf, TESLA technology has been
used in developing cryomodules in collaboration with Stanford
University, housing two cavities operating in cw mode. Gradients of 15
MV/m are routinely achieved in operations.

The 4GLS project is based on an energy recovery linac (ERL) using cw
scrf. An ERL prototype (ERLP) is being constructed at Daresbury, using
accelerating systems with two TESLA cavities per cryomodule to provide
up to 30 MeV energy gain from the 2m active RF structures.

The BESSY Soft X-ray FEL proposes to use a single-pass cw SRF linac
based on developments of the TESLA technology to achieve 15-20 MV/m
accelerating gradient, to accelerate electron bunches up to 2.3 GeV,
with a beam power of up to 150 kW.

KEK has developed two single-cell, 508 MHz, 1.4 MV (5.6 MV/m) SRF
deflecting (crab) cavities for installation in the KEK B-factory in
2005.

> 7\. RIA Cavity and Cryomodule Test Facilities
>
> The U.S. Rare Isotope Accelerator Project (RIA) will include the
> construction of roughly 500 superconducting cavities of as many as 10
> different types to accelerate ions over a velocity range 0.02 \< β \<
> 0.85. These cavity types will include TEM-class cavities such as those
> shown in Figure 6. RIA will require facilities to clean and test the
> individual cavities and also facilities to clean, assemble, and test
> cavity strings and cryomodules. Not all of these facilities need be at
> the RIA site, and some could in principle be included in SMTF. This
> said, however, proximity to the RIA site would be useful in
> simplifying transport and storage
> issues.![](media/image7.jpeg){width="4.118055555555555in"
> height="3.44375in"}
>
> Recent development of TEM-class, drift-tube cavities for RIA has
> achieved new levels of performance by adapting ultra-clean surface
> preparation techniques originally developed for TESLA
> velocity-of-light structures to TEM cavities. This convergence of SRF
> technology of low-velocity structures with that of high-velocity
> structures opens a possibility of a processing and test facility being
> able to serve the needs of both communities.
>
> If SMTF can in fact be structured to accommodate such a broad range of
> cavity types, it would be a unique facility in bringing together under
> one roof the practitioners of several different types of SRF
> technology. The opportunity thus afforded for discussion and sharing
> of technical problems and solutions on a daily, nuts and bolts level
> amongst groups with different experience and perspective could create
> a fertile and creative environment for SRF development.
>
> Within the RIA project there will be several classes of task that
> could possibly be accommodated at SMTF:

1)  Cleaning and cold-testing of individual cavities, after chemical
    processing

2)  Clean assembly of cavities into cavity strings, forming a sealed
    assembly including RF couplers, beam line valves, and vacuum
    manifold and valves.

3)  Assembly of cryomodules incorporating the cavity strings.

4)  Cold test of assembled cryomodules.

> A number of resources will be required to perform the above tasks at
> SMTF. Some are similar to those required for other groups of users,
> such as clean areas with provision for ultrasonic cleaning and high
> pressure rinsing with ultra-pure water and clean storage for cavities
> and associated components.
>
> Because RIA uses low-frequency cavities which can operate at higher
> temperatures than velocity of light structures, 4 K refrigeration at
> the level of a few hundred watts will be needed for both single-cavity
> and cryomodule cold-test capability. For single-cavity tests the
> ability to operate at 2 K is needed, and also possibly for cryomodule
> tests with 805 MHz elliptical-cell
> cavities.![](media/image8.jpeg){width="5.115277777777778in"
> height="1.6666666666666667in"}
>
> Single-cavity test cryostats and cryomodule test areas will need a
> 10-ton overhead crane for set-up and assembly, and will required 18
> inches or more of concrete shielding or equivalent to shield the
> x-rays resulting from high-field operation.
>
> CW RF power at the level of 1-2 kilowatts will be required at several
> different frequencies to test the different types of cavities
> required. A single-cavity test cryostat can be designed to test most
> if not all of the different cavity types and frequencies, but several
> RF sources will be required. For one of the configurations of the RIA
> driver being considered, RF power at 57, 115, 172, and 345 MHz would
> be needed
>
> The facilities for RIA would overlap to some extent with those
> required for the front end of the proposed FNAL proton driver, which
> will also require TEM-class cavities operating at 4.2K. The principal
> difference is that for the proton driver the cavities will be operated
> in a pulsed mode rather than cw, but the cavity types, cryomodules,
> couplers, and tuners are likely to be similar in design.
>
> Table 7.1 shows the resources that will be needed for various tasks
> during the construction of RIA, which is expected to extend over three
> year period. In addition to the floor space detailed in Table 7.1,
> some area, possibly a few thousand square feet, will be needed for the
> storage of incoming parts and sub-assemblies. The lab and office space
> are for a cryomodule test and assembly team estimated at 30 -- 35
> people.

# 8. Electron beam: Fermilab/NICADD Photo Injector and Upgrade

Introduction

Since 1992, Fermilab has been engaged in the production of
high-brightness electron beam[^1]. In conjunction with the TESLA
collaboration, it has constructed and operated an L-band (1.3 GHz) photo
injector, a copy of which was installed at the TESLA test facility in
DESY Hamburg, for various tests, especially for the proof-of-principle
UV SASE free-electron laser experiment[^2]. The Fermilab/NICADD photo
injector laboratory (FNPL) is used as a test facility for beam dynamics
studies associated to high brightness beam and its associated diagnosis,
along with application to advanced accelerator physics.

The photo-injector will be moved to SMTF and will be upgraded in a
phased approach. The present plan at AØ is to reconfigure the injector
to include: a normal conducting gun, and two TESLA cavities (one
operating at 12 MV/m and one at 25 MV/m). This configuration requires a
high power klystron/modulator system (\~4-5 MW) for the normal
conducting gun, and two low power systems (\~300 KW nominal each) for
the two TESLA cavities. Both the gun and the modulator would need to be
upgraded for 5 Hz long pulse operation.

A further step would incorporate two 3.9 GHz cavities of two different
designs, presently under development. One of these cavity types (3^rd^
Harmonic) is operated in deceleration mode and linearizes the beam bunch
energy with time[^3]. The other operates in a deflecting mode[^4] and is
used as a diagnostic to measure beam properties within the different
time slices of the beam bunch. The cavities require \~4 kW power. To
implement these two cavities requires two additional low power
modulators; one of which is similar to that needed for the individual
TESLA cavities (above), and one that is a gated CW modulator.

Eventually it might be desirable to upgrade the injector to a system
similar to that now at TTF[^5]. The two TESLA cavities would be replaced
by an eight cavity module with some of the cavities operating at
\~12MV/m and the rest at\~25 MV/m. Alternatively the module could be in
addition to the two cavities, and installed downstream of them. This
module would require a high power (5 MW) klystron/modulator system. The
one 3.9 GHz decelerating cavity would be replaced by a module of four
3^rd^ Harmonic cavities and would require an 80 KW klystron that could
actually be the same unit as before, but operated at higher power.

Facility and existing capabilities

FNPL consists of a 1+1/2 cell L-band RF-gun equipped with a high quantum
efficiency Cesium-Telluride photo-cathode allowing the photo-emission of
electron bunches with charge up to \~15 nC. The generated bunches are
further accelerated, up to 16 MeV, by a downstream superconducting TESLA
cavity operating with a nominal accelerating gradient of \~12 MV/m (see
Fig.8.1). Downstream of the cavity the beam line includes a set of
quadrupoles and steering dipoles elements for beam focusing and orbit
correction, a skew quadrupole channel that allows the generation of flat
beam using an incoming angular-momentum dominated beam, and a magnetic
bunch compressor chicane which can enhance the bunch peak current up to
approximately 2.5 kA. The diagnostics for measuring transverse beam
properties consist of electromagnetic beam position monitors, optical
transition radiation (or YaG) screens (for measuring beam transverse
density) and three emittance measurements station based on the
multi-slit mask technique. The bunch length measurement is performed by
a streak camera that streaks optical transition radiation pulses emitted
by the bunch. An alternative frequency-domain bunch length diagnostics
based on Martin-Puplett interferometer of coherent transition radiation
is also available. Downstream of the beamline, the beam can be bent in a
dispersive section, to measure the beam energy distribution, or
transported in a straight ahead user experimental area. The FNPL
facility can be operated remotely. So far teams from LBNL and DESY have
used this capability to remotely perform beam physics experiments.

![](media/image9.png){width="5.250694444444444in"
height="2.0527777777777776in"}

Figure 8.1: Overview of the FNPL facility in its present configuration
in the AØ building at Fermilab.

Current activities

Several advanced beam dynamics and beam diagnostics activities are being
actively pursued at the FNPL photo-injector. Our main current efforts
are (1) photo-injector production of angular-momentum-dominated electron
beams[^6] and subsequent generation of a flat beam with high transverse
emittance ratio[^7], (2) longitudinal beam dynamics studies using a two
macro-particle bunch[^8], (3) study of emittance control versus shape of
the photo-cathode drive-laser, (4) emittance evolution of highly charge
electron bunches for different photocathode laser parameter, and (5) R&D
on instrumentation (currently characterization of a bunch length monitor
based on coherent transition radiation). All these experimental studies
also involve theoretical and numerical modeling.

Collaborators from NIU and UCLA have been performing experiment on
plasma-wake field acceleration. The experiment consists of injecting a
high charge (typically 10 nC) short (typically 3 ps) electron bunch in
Argon plasma. The experiment has both concentrated on demonstrating beam
plasma deceleration and acceleration. From this experiment the amplitude
of the accelerating plasma wake-field has been measured to be 130 MV/m.
Our UCLA collaborators have recently installed an experiment devoted to
realize an electron source based on the so-called plasma-density
transition. A first set of experiments were attempted[^9] and the
experimental apparatus is now being used to study focusing properties of
a plasma lens operating in the under-dense regime.

A team from the University of Rochester has developed a laser
functioning on the TM01\* mode, a mode with a longitudinal electric
field component. The laser is now ready and we plan, after the foreseen
energy upgrade of FNPL (see next section), to "couple" the laser and
electron beams with an open iris structure. At energies above 40 MeV, we
will be able to observed laser-based acceleration[^10].

The Urbana-Champaign team will install (in spring 2005) a fast kicker to
make a mockup experiment aiming to test how precise the rising time of
the kicker can be measured[^11]. A fast kicker prototype being
considered for a short damping ring design will then be installed and
characterized with beam.

A collaboration consisting of NIU, University of Rochester and FNAL has
started a program aimed to measure bunch length and time profile of
sub-picosecond bunch using the electro-optical sampling technique. Our
current objective is to re-install, during spring 2005, the original
experiment performed at FNPL[^12] and then gradually improve the
experimental setup.

Upgrade Plans

The TESLA collaboration has recently offered to provide a second TESLA
cavity with an accelerating above 30 MV/m. We plan to install this
second cavity downstream of the first one to boost the beam energy to
approximately 45 MeV. Such an energy increase (by a factor \~3 compared
to the present setup) will considerably reduce the impact of
space-charge forces ($\frac{1}{\gamma^{2}}$) on the beam dynamics and
thereby resulting in a better control of transverse envelope and
emittance. The FNPL upgrade will also allow the support of variety of
"user experiment" discussed later in the present Chapter.

In the process of this beamline extension, and given the space
constraint in the AØ building, we currently plan to also configure the
beamline to allocate room for one of the 3.9 GHz cavity being developed
at FNAL (either the deflecting or accelerating mode). The deflecting
mode cavity was initially designed in the context of the Kaon separation
out of the secondary beam produced at the main injector at FNAL
(so-called CKM experiment). It has also applications in the LUX proposal
at LBNL[^13] to generate ultra-short X-ray pulses. The accelerating mode
cavity was developed to linearize the longitudinal phase space prior to
a magnetic bunch compressor[^14] and thereby enhance the peak current
(after magnetic compression) in an accelerator working on the 1.3 GHz
frequency. Such a "linearizer" has applications in the context of light
source (TESLA VUV/X-ray FELs, LUX project at LBNL, etc...) and also
linear collider (TESLA post damping ring bunch compressor[^15]).

![](media/image10.png){width="5.991666666666666in"
height="2.229861111111111in"}

Figure 8.2: Overview of the upgraded FNPL facility. The facility will
incorporate two TESLA cavities, and a location for testing any of the
two 3.9 GHz cavities being developed at FNAL.

At FNPL the use of the deflecting mode cavity would provide a unique
diagnostics that would allow the measurement of beam parameters within
the bunch (so-called slice parameters) and result in a more complete
picture of the beam dynamics of space-charge-dominated electron beams. A
schematic of the proposed FNPL upgrade is shown in Figure 8.2.

FNPL upgrade as an e- injector for SMTF

In the context of SMTF, the upgraded version of FNPL would provide an
ideal injector that could, at a later stage, be transplanted on the SMTF
site. We envision three phases for the photo-injector (see Figure 8.3):

-   Installation of the FNPL upgraded injector on the SMTF site (phase
    A),

-   Installation of a 3.9 GHz rf-system (both an accelerating and a
    deflecting mode cavities) in the injector (phase B),

-   Replacement of the injector cavities by an eight-cavity accelerating
    module (phase C).

We now describe each of the injector phase with their capabilities in
more details. It should be noted that the detailed numerical simulation
and optimization of the different stages have not yet been completed.

![](media/image11.png){width="5.997222222222222in"
height="3.3055555555555554in"}

Figure 8.3: proposed staged upgrade for the photo- injector. The FNPL
energy upgraded injector will be installed upstream of a cryomodule (A).
The 3.9 GHz accelerating and dipole mode cavities will be incorporated
in the injector (B). At a later stage, the accelerating section (two
TESLA cavities) of the injector will be replaced by a standard 8-cavity
accelerating module.

**[Injector Phase A:]{.underline}** A configuration consisting of an RF
gun followed by the two TESLA cavities, as planned to be operated at
FNPL, would provide a transverse emittance-compensated beam. According
to preliminary numerical studies, such a beam could then be subsequently
accelerated by a TESLA accelerating module operated at any accelerating
gradient without significantly impacting the transverse emittance. Such
a feature means that an injector consisting of an rf-gun with two TESLA
cavities only (in the present case operated at 12 and 25 MV/m average
accelerating gradient) would be an independent entity that could provide
controllable beam parameters to be injected in SMTF. The current FNPL
facility (one RF-gun followed by one TESLA cavity) does not provide such
a capability: the beam is still space-charge-dominated: even over a
short drift the beam parameters tend to degrade. Therefore FNPL upgrade,
while enabling the extension of the current advanced accelerator physics
program, could also be viewed as the first phase of SMTF. Parametric
studies and subsequent optimization of the system should allow the
production of high quality beam. The FNPL upgrade will also provide
operational experience (e.g. with a new rf-control system) and training
for future scientist working at SMTF. We anticipate the upgrade of FNPL
(to be ready for SMTF) to include: the installation of the TESLA cavity
offered by DESY, an upgrade of the photocathode drive-laser[^16] (to
improve the reliability of the facility), an upgrade of the modulator,
an improved RF gun, to support greater beam duty factor and minor
upgrades of the beamlines (especially the bunch compressor and the
spectrometer dipole). We should note that the only presently foreseen
difference between SMTF injector phase A and FNPL upgrade might be the
location of the rf-gun and the first accelerating cavity (this is based
on extensive simulation work done for XFEL injector at DESY[^17]).

The upgraded version of FNPL \[along with space allocation for the 3.9
GHz cavities (see phase B)\] will take about 20 meters (distance
referenced with respect to the cathode), we therefore need additional
magnets to transport the beam up to the accelerating module (straight
section located between the spectrometer and the entrance of the
accelerating module in Fig. 8.3 A). We suggest specifying the magnets
(quadrupole and corrector magnets) for a beam energy of \~200 MeV. Such
magnets could then be reused in phase C for the bunch compressor area
located downstream of the first accelerating module (see Fig. 3 C). The
detail transport has not yet been worked out but we suggest the use of
15 quadrupoles and 7 pairs of steerers \[these numbers are also based on
preliminary consideration for phase C (including spares)\].

**[Injector Phase B:]{.underline}** A second phase of the injector will
include the two 3.9 GHz cavities being developed at FNAL. The
accelerating cavity together with the magnetic bunch compressor located
before the accelerating module (schematic B in Figure 3) will provide
SMTF with high peak current bunches that could be use for wakefield
measurement or for user applications (e.g. laser or plasma wakefield
acceleration) after accelerating in the module. The deflecting cavity
will be installed just downstream of the bunch compressor and will
provide measurement of the bunch length and slice parameters within the
bunch. It will also serve as a diagnostics for properly setting the 3.9
GHz accelerating cavity phase and amplitude for optimum compression.
Apart from minor beamline reorganization we do not expect other major
changes.

**[Injector Phase C:]{.underline}** The final stage of the injector
evolution will consist in replacing the accelerating section and low
energy transport and diagnostics sections by a standard accelerating
module (schematics C in Figure 8.3). At this stage the bunch after
generation in the rf-gun will be directly injected in an accelerating
module and accelerated to approximately 150 MeV. The bunch will then be
compressed using a magnetic chicane and further accelerated in the
second (original) accelerating module. Such a configuration will be
similar to the TTF VUV FEL injector. The installation of a 3.9 GHz
accelerating module (consisting of four cavities) prior to the bunch
compressor will enable the generation of high peak current electron
bunch. The magnets used in phase A and B between the spectrometer and
entrance of the original accelerating module will be recycled in phase C
for the optic needed in the bunch compressor area (see Fig 8.4).
Presently we envision the bunch compressor area to include 3 triplets
for transverse beam size control before and after the bunch compressor,
and a round-to-flat beam transformer consisting of (3 or 4) quadrupoles
enabling the production of flat beam from an incoming magnetized beam.
For phase C, we will need to upgrade the bunch compressor dipoles to be
able to bend the higher energy beam (150-200 MeV in phase C compared to
40-50 MeV in phases A and B). The high energy dumps located downstream
of the second accelerating section should be specified for 1 GeV (up to
about 1.3 GeV) so to be also usable downstream of the fourth module (ILC
test string) at a latter stage of the SMTF project.

![](media/image12.png){width="6.123611111111111in"
height="2.342361111111111in"}

Figure 8.4: Overview of a possible layout for the final stage of the
injector (phase C). The distances (in meter) are estimates based on the
TTF VUV FEL design.

In parallel to the staged evolution of the injector (phases A to C), we
strongly recommend the development and construction of a new symmetric
RF-gun cavity similar to the one in operation at the TTF VUV FEL
facility[^18]. The latter rf-gun could be installed in the SMTF injector
at any stage.

As presently conceived the CW module would be located downstream of the
β = 1 accelerating modules in the region called experimental area.

The RF power Requirements for each injector phase are:

-   Phase A- one 15 MW modulator (B2), one 5 MW klystron

    -   two 600 KW modulators (S1, S2), two 300 KW klystrons

-   Phase B- Phase A plus -- one 600 KW modulator (S3), one 80 KW 3.9
    GHz klystron

    -   one 6 KW special modulator (SS4), one 3KW 3.9 GHz kly

-   Phase C- two 15 MW modulators (B2, B4 new), two 5 MW klystrons

    -   The two 3.9 GHz systems as above in Phase B.

Injector Phase A, B

-   Finish building one 170 KW modulator (S3),

-   Rebuild two 300 KW klystrons

Injector Phase C

-   Build one new prototype modulator

-   Procure one 10 MW multibeam klystron

[Injector RF Systems Table]{.underline}

<table>
<colgroup>
<col style="width: 12%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 0%" />
<col style="width: 17%" />
<col style="width: 0%" />
<col style="width: 14%" />
<col style="width: 0%" />
<col style="width: 13%" />
<col style="width: 0%" />
<col style="width: 14%" />
<col style="width: 0%" />
<col style="width: 14%" />
<col style="width: 0%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="2">System</td>
<td colspan="2">Phase</td>
<td colspan="2">Cavity</td>
<td colspan="2"><p>Klystron</p>
<p>nominal power</p></td>
<td colspan="2">Klystron status</td>
<td colspan="2">Modulator</td>
<td>Modulator status</td>
<td></td>
</tr>
<tr class="even">
<td>Injector</td>
<td colspan="2">1</td>
<td colspan="2">NC gun</td>
<td colspan="2"><p>Thales</p>
<p>TH2104C</p>
<p>5 MW</p></td>
<td colspan="2">Exists</td>
<td colspan="2"><p>15 MWatt</p>
<p>“Big”</p></td>
<td colspan="3"><p>exists</p>
<p>needs upgrade</p></td>
</tr>
<tr class="odd">
<td></td>
<td colspan="2"></td>
<td colspan="2">Tesla cavity 1</td>
<td colspan="2"><p>Phillips</p>
<p>YK 1240</p>
<p>300KW</p></td>
<td colspan="2">Exists</td>
<td colspan="2"><p>600 kWatt</p>
<p>“Small 1”</p></td>
<td colspan="3">exists, planning to rebuild</td>
</tr>
<tr class="even">
<td></td>
<td colspan="2"></td>
<td colspan="2">Tesla cavity 2</td>
<td colspan="2"><p>Phillips</p>
<p>YK 1240</p>
<p>300KW</p></td>
<td colspan="2">exists, under rebuild</td>
<td colspan="2"><p>600 kWatt</p>
<p>“Small 2”</p></td>
<td colspan="3">under fab/parts procure</td>
</tr>
<tr class="odd">
<td></td>
<td colspan="2"></td>
<td colspan="2">3<sup>rd</sup> Harmonic</td>
<td colspan="2"><p>CPI VA 908K2</p>
<p>80 KW</p></td>
<td colspan="2">In fabrication</td>
<td colspan="2"><p>600 kWatt</p>
<p>“Small 3”</p></td>
<td colspan="3">under fab/parts procure</td>
</tr>
<tr class="even">
<td></td>
<td colspan="2"></td>
<td colspan="2">3.9GHz Def (CKM)</td>
<td colspan="2"><p>CPI VKC 7810F</p>
<p>3KW</p></td>
<td colspan="2">Exists</td>
<td colspan="2">“ CW”</td>
<td colspan="3">under fab</td>
</tr>
<tr class="odd">
<td>Injector</td>
<td colspan="2">3 same as 2 with upgrade</td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="2"></td>
<td colspan="3"></td>
</tr>
<tr class="even">
<td>Injector upgrade 1.3</td>
<td colspan="2">3</td>
<td colspan="2">8 cavity module</td>
<td colspan="2"><p>Thales</p>
<p>TH2104C</p>
<p>5 MW</p></td>
<td colspan="2">need or use TH2095A</td>
<td colspan="2"><p>15 MWatt</p>
<p>“Big”</p></td>
<td colspan="3">Need</td>
</tr>
<tr class="odd">
<td>Injector upgrade 3.9</td>
<td colspan="2">3</td>
<td colspan="2">4 cavity 3rd Harmonic 3.9GHz module replaces single
cavity</td>
<td colspan="2"><p>same RF as before</p>
<p>CPI VA 908K2</p>
<p>80 KW</p></td>
<td colspan="2">may need 2nd Klystron</td>
<td colspan="2"><p>same mod as before</p>
<p>600 kWatt</p>
<p>“Small 3”</p></td>
<td colspan="3"></td>
</tr>
</tbody>
</table>

9.  Cavity and Cryomodule Fabrication Infrastructure

Considerable superconducting cavity and cryomodule infrastructure exists
and is spread amongst a number of US laboratories. Nevertheless
substantial upgrades are needed at these facilities and at Fermilab in
order to develop and exploit state-of-the-art advances in SRF
technologies. We intend to build upon the existing infrastructure in a
collaborative way to construct several cryomodules. The SMTF concept is
based on collaboration between industry, laboratories and universities.
Resources and expertise will be shared. The SMTF collaboration has
developed and agreed to a cavity and cryomodule fabrication plan that
utilizes the existing distributed infrastructure and identifies the
needed upgrades. This plan significantly minimizes the cost and advances
the schedule. This plan is expected to evolve once the process has
begun.

We propose to build the dressed US cavities as a collaboration of
industry, Cornell University and Jlab. Initial cavity fabrication and
vertical testing will be led by Cornell in collaboration with industry.
The cavities would be electro-polished at Jlab. JLab will dress the
cavities and send them to Fermilab. The infrastructure at Cornell and
JLab will need upgrading. In order to carry out the SMTF program
outlined in this proposal, the infrastructure at Fermilab will need to
be substantially augmented. The near term Fermilab infrastructure will
include a horizontal test stand and the capability to assembly cavities
into strings for insertion into cryomodules.

The long term goal is to have the overall general capability to carry on
a small research program and have the capability to prepare, process
(chemical and electropolish), and test (vertical and horizontal)
cavities at the level of one to two per month, consistent with a limited
research and development program.

In discussion with the collaborating institutes we have developed a plan
for the near term. This plan addresses how to proceed on two modules,
the DESY-Fermilab and ILC modules. The parts for the DESY-Fermilab
module will be supplied by DESY. The most feasible plan at this point
appears to have DESY test the dressed cavities in their CHECHIA cryostat
(single cavity horizontal test cryostat) and then ship the tested and
sealed cavities to Fermilab. In addition they ship the additional
components needed to build the full cryomodule. At Fermilab, the dressed
cavities are assembled into eight cavity strings, mounted to the helium
header and assembled into the cold mass outer cryostat.

The critical part of this assembly takes place in a class 10 clean room
environment. The cavities exteriors must be cleaned of particles before
entering the clean room, then the end flanges carefully removed and
cavities, bellows, gate valves, and quadrupole assembled under best
achievable clean room procedures. This is a step that will give
important learning experience to the Fermilab assembly staff. Once the
ends of the string are sealed, the string can be removed from the clean
room. The string is mounted to the 300 mm helium header and the tuners
and magnetic shielding is mounted. Then the assembly is inserted into
the outer cryostat vacuum vessel and the warm parts of the couplers are
mounted.

The main infrastructure needed for the proceeding operations is:

-   A class 10 clean room of about 10 ft x 50 ft

-   Particle free vacuum and leak detection equipment

-   Miscellaneous Clean Room support equipment (e.g. Ultra Pure Water,
    Ultra Sound tanks, Nitrogen gas, particle detectors, etc). and for
    the string and module assembly

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-   Miscellaneous fixtures and tooling.

Fermilab will develop a cryomodule assembly facility at MP9. This is the
minimal investment needed to assemble cryomodule module and is discussed
in more detail in the cryomodule assembly section.

The plan for the first ILC module is as follows: It is expected that 4
cavities for the "1^st^ ILC module" will be produced in a
Cornell-Industrial collaboration. The other 4 cavities will come from
KEK. Once the cavities have passed the vertical dewar test at Cornell,
they will be sent to JLab for Electropolishing (EP), vertical test and
dressed. Once the test is successful, JLab will then mount the helium
vessel, HPR and assemble flanges and the cold input coupler part to
ready the cavity for horizontal test. At this point the cavity will be
shipped to Fermilab for test in the Horizontal Test Dewar. A similar
procedure will be followed for the KEK bare cavities. Oven treatment of
the cavity at high temperature is still being discussed.

The new infrastructure needed at Cornell and JLab to get started in this
way is minimal. Cornell has the necessary infrastructure except an 800
degree oven for hydrogen removal prior to final BCP. JLab has such an
oven and cavities will be shipped to Jlab for this step. At JLab
commissioning of their EP system is on going. It will be necessary to
modify it for the TESLA cavity size and make other special modifications
to their processing infrastructure. It is expected that these
modifications will take place in FY05 and the tests of the EP process
will begin on cavities supplied by DESY.

There is no 1.3 GHz Horizontal Test Dewar (HTD) in US so Fermilab will
build this and use RF power from one of the "small modulators" installed
in the Meson Hall. It is expected that fabrication of the HTD will start
in FY05, and the small modulator will be available after the single
Capture Cavity test at the end of FY05.

There also exists minimal SRF infrastructure at FNAL. If additional
funds are available Fermilab should continue to develop its own SRF
infrastructure. The present infrastructure Fermilab located at A0
consists of:

-   Soft wall clean room of 16ft x 24 ft (entry area, \~200 sq ft class
    100, \~100sq ft class10)

-   Ultra Pure water system (1000 gallon storage)

-   High Pressure Water Rinse system

-   Miscellaneous equipment and ultra sound.

-   Vertical dewar for 3.9 GHz test

Argonne and Fermilab have been collaborating on a chemistry facility
located at ANL. This facility should be completed in FY05. Commissioning
of the FNAL BCP system for 3.9 GHz cavities should take place in FY05 as
well. Adaptation of the system for TESLA cavities should start in FY05,
but initial treatment of TESLA cavities will probably not start until
FY06.

On a longer scale it is hoped that with the help of KEK we will be able
to implement a horizontal EP system at the Argonne facility. This then
will give the US two such processing systems one at JLab and one at ANL.
The cost of such a system may mean that it will be some time before it
can be implemented. However it is important to have alternative systems
for a reliable fast turnaround cavity development program.

The above discussion outlines a minimal program to get started with the
assembly of two modules from cavities that have been processed and
prepared elsewhere. The intension is that this model will continue with
some modification for the fabrication of cavities and modules past the
first couple. Fermilab should continue to develop its own SRF
infrastructure and gain capability not only in module assembly but in
cavity processing and testing as well.

The goals of this further infrastructure development are to:

-   Continue infrastructure development to support the ongoing 3.9 GHz
    cavity development as well as TESLA cavities

-   Bring to FNAL the ability to carry out an R&D program of process and
    test of ILC and Proton Driver cavities at a rate consistent with a
    relatively modest development program. (Of order 2 cavities/month).
    For instance this infrastructure should provide a reasonable and
    efficient turnaround time between test and reprocess and retesting
    of cavities

-   Position FNAL so it (as well as JLab and Cornell) has the knowledge
    and expertise to direct and assist industry in the manufacturing,
    process, test, and assembly steps for industrialization and
    production.

-   Provide at an adequate level, redundant processing capability to
    that existing at JLab so as to avoid schedule slips brought on by
    processing equipment failures or contamination leading to long
    duration recertification of the processing performance for achieving
    high gradient cavities.

Phase 2 SRF Infrastructure

During Phase 2 many of the activities described above will continue with
miscellaneous upgrades, improvements and ongoing operational expenses.
Three major new investments are contemplated in Phase 2 that will give
FNAL the capability learn and perform high performance cavity
preparation and certification.

[Vertical Dewar]{.underline}

The vertical dewar CW RF test of bare cavities after fabrication is a
key check of cavity gradient performance. Though a number of labs have
this capability, it is important that Fermilab also obtains this ability
so as to have rapid turnaround between chemical treatment and the
resulting cavity performance. Fermilab designed and built two such dewar
systems for the TESLA collaboration a number of years ago.

[Chemical processing- ElectroPolishing]{.underline}

On a longer scale (Phase 2) it is hoped that with the help of KEK we
will be able to implement a horizontal EP system at the Argonne
facility. This will give the US two such processing systems one at JLab
and one at ANL. The cost of such a system may mean that it will be some
time before it can be implemented. However it is important to have
alternative systems for a vigorous cavity development program. At some
time such a system might become part of an industrial-lab cooperative
activity.

[Electron-Beam Welder]{.underline}

E-Beam welding is fundamental to cavity fabrication. The TESLA TDR cost
estimate study recognized the possibility of major cost savings in
cavity fabrication costs with a welder specifically designed for
efficient cavity production. In the US there will need to be a dedicated
welder(s) for ILC cavity production. Such a welder is not presently
available and may make fabrication of cavities at a reasonable rate very
difficult. Various laboratories have welders but they are in demand for
a variety of projects. Industrial welding capability is very limited and
it is extremely difficult to find dedicated machines.

[Industrial Studies and Industrialization]{.underline}

It will be important to begin some level of industrial contact (beyond
fabrication contracts) as soon as possible. This involvement should be
at minimum include industrial studies, and participation with
laboratories in module processing, test, and assembly. It should lead up
to planning and prototyping of tooling etc for preproduction industrial
activities. For ILC development this effort will clearly fall to the
purview of the ILC coordination. However we include minimal funds in
this proposal to indicate the importance of initiating the
industrialization.

[SRF Cryomodule Assembly Facility at MP9]{.underline}

The Fermilab cryomodule assembly facility will provide the
infrastructure for the assembly of the SRF cryomodules. MP9 has no
cryogenic capability and therefore it will only be used as a mechanical
assembly facility. High power RF and beam testing of the completed
cryomodules will be conducted at the Meson Lab test facility.

MP9 is intended to be an R&D production area. Based on DESY\'s
experience, the first cryomodule is expected to take 3 to 4 months for
assembly. The assembly of subsequent cryomodules is expected to take 3
to 4 weeks based on the experience from DESY for TESLA cryomodules and
JLab for SNS cryomodules.

The Tesla Test Facility (Hall 3) layout at DESY was used as a reference
while preparing this preliminary study for an SRF cryomodule assembly
facility at MP9.

[Assumptions:]{.underline}

The following assumptions were made in order to generate the production
workflow for the SRF cryomodules at MP9:

SRF bare cavities are fabricated in industry. (Form/machine parts,
electron beam welding)

-   Cavities are processed (tuned for field flatness, baked, chemical
    etched, electro-polished, high pressure water rinsed) and vertical
    dewar tested. Then they are outfitted with a helium vessel, an input
    power coupler, and further dressed (tuner, magnetic shielding,) for
    the horizontal dewar test. It is assumed that these steps are not
    carried out at MP9 . After passing this test the cavity with helium
    vessel and cold part of the input coupler is delivered sealed to the
    MP9 facility.

-   The sealed cavities with cold input coupler are received at the MP9
    facility for incorporation into cryomodules.

Production Work Flow of the 1.3 GHz Cryomodules**[:]{.underline}**

Given the assumptions listed in the above paragraph, the work flow steps
to assemble a cryomodule can be generated, and the required
infrastructure and tooling /fixtures associated with each step
determined. The production steps and related infrastructure are shown in
Figure 9.1 and summarized below as:

[Receiving & Storing Dressed Cavities / Peripheral Parts:]{.underline}

1.  

Processed and dressed cavities will be stored at the Receiving & Storage
area. The sealed cavity interiors have been backfilled with dry nitrogen
or argon, while no special precautions other than bagging are taken with
the cavity exteriors. The cavities are stored in their shipping
containers on the storage racks until use. Peripheral components
required for assembly of a cryomodule (such as warm coupler parts,
tuners, magnetic shielding, vacuum vessel, cold mass components, and
cryogenic piping, instrumentation, and alignment system components) will
be stored in this area as well. An accurate inventory of all stored
parts will be maintained, and a traveler system will assure proper
material control procedures are followed for each kit of parts withdrawn
from storage for the construction of a cryomodule. The footprint of the
storage area is 60 ft x 60 ft. The area shall be clean for an industrial
area. It will contain racks and shelves for storage of dressed cavities
in their shipping containers, as well as peripheral parts kits. The area
shall be situated to permit full semi-trailer truck access. The area
shall have total crane coverage of at least 20-ton capacity.

[Cavity String Assembly:]{.underline}

The sealed cavities are brought into the class 10 clean room assembly
area and assembled into a cavity string in the Cavity String Assembly
area. A string consists of 8 dressed 1.3 GHz cavities aligned and
connected together. The cavities will be removed from their shipping
containers, installed on a transport cart and washed to reduce the dust
particle contamination on the outer surface prior to moving them into a
Class 10 clean room. The Cavity String Assembly Class 10 clean room
dimensions shall be at least 50 ft x 10 ft. It will have a cavity
support, alignment and transportation rail fixture system.

[Cryomodule Assembly:]{.underline}

The Cryomodule Assembly area is divided into two parts: (1) a Cold Mass
Assembly area adjacent to the Cavity String Assembly clean room where
the completed cavity string is integrated into the cold mass (defined as
everything in the cryomodule except the cavity string and the vacuum
vessel: including the cryogenic piping, radiation and super-insulation
shields, cavity magnetic shields, alignment system, etc.) and (2) a
Vacuum Vessel Assembly area where a large, cantilever fixture is used to
install the cold mass/string assembly into the vacuum vessel. The
footprints required are: 100 ft x 30 ft for the Cold Mass Assembly area
and 160 ft x 10 ft for the Vacuum Vessel Assembly area.

A Tesla Cryomodule + lifting fixtures weigh over 8 tons, thus one needs
at least 20 ton crane coverage for the whole Cryomodule Assembly area.
MP9 has a 25 Ton crane.

[Infrastructure and Tooling Setup at MP9**:**]{.underline}

The proposed layout of the Cryomodule Assembly Facility at MP9 can be
seen in Figure 9.2. The major infrastructure needed for the assembly
areas are clean rooms. One can summarize the needed major infrastructure
as follows:

MP9 has a readily available production floor space a 25-ton crane is
present in the building. We will need to purchase a variety of clean
rooms and tooling fixtures for the

Various areas.

**Work Flow at MP9**

# 

Figure 9.1 Flow of cavity to cryomodule at Fermilab MP9 Facility

[Summary:]{.underline}

The MP9 building will be used for the cryomodule assembly facility.

# Clean rooms and infrastructure are being procured. The tooling and fixtures. designs are being provided by DESY. 

# ![](media/image13.jpeg){width="5.625in" height="8.0in"}

## Figure 9.2: Possible Layout of the Cryomodule Assembly Facility at MP9

10\. SMTF Facility

a\. Meson East Infrastructure

We describe in this chapter the plan, cost and schedule for the
conventional and some technical infrastructure for the SMTF test area in
the east beam lines of the Meson Hall. Conventional infrastructure
includes space, shielding, utilities, such as electrical power, water
and HVAC. The technical infrastructure included here is limited to the
controls and communication backbone, and equipment for safety and
radiation management. Other technical infrastructure, such as RF power
sources and cryogenics are covered elsewhere in this proposal.

# i. Space in Meson Hall

The east side of Meson Hall, comprising two adjacent beam lines, ME and
MP, has not been used for experiments for a number of years. The west
side of Meson Hall is presently used for test beams, and the center beam
line (MC) is in use for an active experiment. Present plans indicate
that the MC beam line may be in use indefinitely, which restricts the
space available for SMTF.

The appeal of Meson East rests on the availability of two important
resources: a refrigerator capable of delivering at least 60 watts at 2 K
exists and is operational, along with a cryogenic transfer line that
extends from the refrigerator almost to the Meson East area; and the ME
beam line is quite long and could be lengthened without major
construction. In addition, a 20-ton crane covers the detector building,
making installation and maintenance convenient and there is adequate
installed power and water.

There are some disadvantages, however. The Meson East beam line is at
grade level, which will require the installation of massive amounts of
shielding when the beam lines reach full power capability. Moreover, in
recent years Meson Hall has received little care and maintenance, and
has become a storage area for magnets and no-longer-used experimental
equipment. The roof is in some disrepair and there are places where
there are significant water leaks during heavy rains. This problem will
be moderated temporarily with judicious placement of plastic over the
experimental area.

A general disassembly and cleanup is required to make the area useful.
This activity is in progress and will be largely completed in FY2005
except for major items such as roof repair. Further improvements will
extend into the out years, including roof repair, lighting repair and
modernization, refurbishment of the HVAC and chiller systems, as well as
general building maintenance activities.

[Photo injector and 1.3 GHz Beam line Layout]{.underline}

After the cleanup and construction of the beam line caves are complete,
the East area of Meson Hall will look as it does in Fig. 10.1. The East
beam line starts in the South end of the detector building with the
photo injector, laser and beam analysis, and extends northward with the
installation of 1.3 GHz superconducting modules. The plan shown is long
enough to accept the first two long modules. The photo injector and the
first large module are under crane coverage, but subsequent modules will
have to be lowered into the cave onto dollies and wheeled to their
proper position. The inside dimensions of the cave are 15' wide by 10.5'
high and the center of the beam line is slightly offset to the east of
center, resulting in a clear aisle for safety needs and module
installation. The beam line can be extended by the use of shielding
blocks. The steel "worms" may need to be enlarged at the downstream end
of the beam lines.

The laser is in a moderately clean temperature-controlled room as shown
in the Fig.10.2, which also shows the RF modulators and klystrons
distributed along the west side of the shielding cave in convenient
locations. The laser shed may be elevated so that it is not in the way
of other equipment, but in any case its supports will be isolated from
the building and supported on vibration dampers.

[Proton Driver and β\<1 beam line]{.underline}

The ion source for the β\<1 beam line is in the detector building under
crane coverage, but the beam line in this case heads south into an
existing shielded tunnel. This is possible because the length of this
beam line is expected to be short, not exceeding 50 m when fully
developed. Putting the beam into a tunnel reduces the amount of
shielding that needs to be installed. The klystron is shown in the
shielded tunnel, and the modulator is installed immediately outside the
north end of the tunnel. The inside dimensions of the tunnel are roughly
the same as the Meson East tunnel, as shown in Fig. 10.2.

[CW test area]{.underline}

The CW test area will be in a separately shielded cave downstream of the
ME beam line. It can use the β=1 beam for test that require beam. A
separate electron gun source could also be installed, which will make
test scheduling more convenient for all users. The major issue of the CW
test facility is its use of cryogenics. One 1m long module is expected
to require 40 watts at 2 K plus shield loads, so that it would be
difficult to supply beam from the β=1 system simultaneously at 100
percent duty factor. Adequate tests can be performed, however, with a
smaller duty factor so long as the pulse length is long compared to the
cavity fill time. The RF power requirements for this system are small.

[Horizontal test facility]{.underline}

A test facility that can have single modules of any kind connected to it
for cryogenics and beam is also desired in this area. The refrigeration
and power is adequate. It could be set up either near the β\<1 beam line
or even in the ME tunnel. This second location is convenient for
connection to the refrigerator because it is close to the planned
distribution box. RF power requirements are modest for this facility,
and there are no beam requirements.

![](media/image14.jpeg){width="5.9944444444444445in"
height="2.1069444444444443in"}

Fig. 10.1 Cleaned out Meson East area with shielding walls.

![](media/image15.png){width="5.990972222222222in" height="2.13125in"}

Fig 10.2 Meson East area with the addition of modules, modulators,
klystrons and control racks. The CW test area (downstream of ILC) and
the horizontal test facility in the ME tunnel are not shown.

# ii. Conventional Facilities in Meson Hall

[Power Distribution]{.underline}

The power distribution infrastructure must support the planned
modulators and other systems. The power requirements for the β\<1 and
photo injector beam lines including the first two long modules are
easily satisfied with one of the two available 1.5 MVA transformers at
the southeast end of the detector building. The remaining two modules
and the two large vacuum pump skids will be powered off another 1.5 MVA
transformer conveniently located nearer the north end of the detector
hall. One 500 KVA transformer at the south end of meson Hall will be
shielded and will be more than adequate for the quiet power needs of the
controls and low-level RF.

[Water Distribution]{.underline}

The total number of klystrons, solenoid magnets and modulators will
require about 400 gpm of chilled LCW (max temperature \< 35° C at
relatively low pressure, about 100 psi. The detector building LCW system
can easily supply the amount needed at 200 psi, which will have to be
regulated down in pressure and processed through a chiller capable of
maintaining the temperature at the maximum load. Since all of the
systems cannot operate simultaneously, the initial installation can be
made with a smaller chiller.

[HVAC Installation]{.underline}

The requirements for heating, ventilation and air conditioning in the
Hall are fairly modest. The occupied areas of the building are heated
for comfort in the winter months, but air conditioning is supplied only
where required, mostly for closed electronics racks with sensitive
electronic equipment. We will upgrade the rooms along the East wall of
the detector building for electronics and for office space. They will be
temperature controlled. Fans may be required in the shielded caves to
move the air and prevent moisture condensation.

# iii. Technical Infrastructure in Meson Hall

[Controls System Backbone]{.underline}

Rapid implementation of a controls system with characteristics that
allow it to evolve quickly for our needs with minimal personnel effort
is critical. An expert committee has been formed with representation
from outside Fermilab to assess the requirements and make a
recommendation of the system that best meets SMTF needs. This
recommendation will be determined in the near future. Such a system
should rely as much as possible on existing control systems and
applications. By the end of FY 05 we will need the ability to control
the cryogenic system and the RF modulator system for the capture cavity,
and to interface to the low-level RF system and the modulator
control-interlock interface. To set the scale of the control system that
will be needed eventually, it is useful to note that the present TTF
controls has approximately 40 VME crates and timer modules, 900 ADC
channels, many of which are sampled at 1 or 9 MHz during the RF pulse.

[Safety Systems]{.underline}

The safety systems will be configured similarly to the Fermilab
accelerator controls, but will be independent except for monitoring. The
system has three major subsystems: radiation protection, high-power
interlocks and oxygen deficiency hazard protection.

[Radiation Protection]{.underline}

Continuous radiation in the caves arises from four sources: x-rays from
the cavities due to accelerated dark current; electrons from beam loss
that will produce x-rays, gamma rays and neutrons, and, most important,
neutrons from the beam stop. These neutrons have a significant backward
component, making it necessary to shield even upstream of the beam stop.
Single events are not usually a problem because they are detected
electronically and the beam shut off until the cause is fixed.

Radiation protection generally follows the rules and regulations of the
Accelerator Division at Fermilab. The shielding is overlapping light
concrete blocks to eliminate cracks. The design in Fig. 10.1 and 10.2
has 4.5 feet of light concrete in the walls and ceiling of the caves.
The present allowable radiation inside the occupied areas the Meson Hall
is 5 mrem at contact outside the shielding. Calculations are being done
now to determine the amount of shielding necessary to meet that
criterion.

[Electrical Hazards]{.underline}

The modulators and klystrons present potentially dangerous electrical
hazards of high power, high voltage and large stored energy.
Fortunately, Fermilab Accelerator Division has been dealing with similar
hazards for many years and has developed effective protection systems
and procedures to eliminate the dangers. This expertise will, of course,
carry over to the Meson Hall installations.

[Oxygen Deficiency Hazards]{.underline}

Although the Meson Hall is large enough that it presents no oxygen
deficiency hazards under any reasonable occurrence, the smaller volumes
of the radiation caves do present possible hazards. The general
procedure at Fermilab will be followed; training, oxygen concentration
detectors in the space and on the personnel, air packs in enclosed
spaces, and exhaust fans. Helium is probably not as much a problem as
liquid nitrogen, since it can be easily vented with fans. Cold nitrogen,
however, remains near the floor, and is more difficult to vent. In the
longer term, nitrogen flow will probably need to be eliminated from
tunnels and caves. This will probably await the Phase 3 refrigerator
upgrade.

# b. Cryogenics for SMTF at Fermilab

The SMTF collaboration proposes to use the Cryogenic Test Facility (CTF)
refrigerator system at Meson building at Fermilab to supply the initial
helium for the SMTF. It is expected that this system will be capable of
\~60 watts at 2K after its upgrade. This capacity will be sufficient for
Phase 1 operation of SMTF, where we propose to share the cryogenic
between different users. This facility will not support the full program
of SMTF and a Helium plant with a capacity of \~\>300 W at 2K is
required.

Fermilab Cryogenic Department has started working in FY05 to develop the
CTF facility for the Phase 1 operation of SMTF. This work will include:

-   The installation of transfer lines from the refrigerator building to
    the Meson Hall

-   Upgrade of CTF

-   Provision for feed cans for the Capture Cavity Test (a main goal for
    FY05)

-   Cryogenic controls

These upgrades will enable the collaboration to test components at 4K
helium temperatures. Further upgrades are proposed for FY06 with a goal
to operate an ILC 8, 9-cell cavities in a cryomodule in the Meson Hall
at 2 K. This upgrade will require:

-   Installation of a vacuum pumping system

-   The construction of a large feed box and module feed and end cans

-   Construction of the cryogenic transfer line

-   Installation of associated cryogenic controls.

In FY05, the investigation of the best way to proceed with a larger 2K
cryoplant is being pursued. One of the two possibilities is to try to
use parts of the SSC system presently at Argonne National Laboratory. A
second possibility is to procure a modern system specifically built for
2K SRF operation similar to that at Rossendorf (Germany). This new
system is expected to take about 2 years for the procurement,
fabrication and installation. This proposal request funds in FY06 for a
new cryogenic plant with a capacity of \~300 Watts at 2K. As described
in the earlier sections of the proposal this capacity is required to
support cryomodules and test areas. Even at this capacity the different
accelerator groups would be required to share the cryogenics.

Beyond providing cryogenic equipment for a single TESLA cryomodule (in
the ILC string area) by the end of 06, additional cryogenic
infrastructure is needed for the following components:

1.  The photo injector.

2.  Upgrading to four cryomodules.

3.  Providing for test cryostats, e.g. Horizontal and Vertical Test
    Dewars.

4.  Providing for other string areas, e.g. Proton Driver and CW.

5.  Long term upgrade of the injector to a 8 cavity TESLA module with a
    4 cavity 3.9 GHz module.

1\) The first stage of the injector will include two 1.3 GHz Tesla SRF
cavities (CapCav #1 and #2) and two 3.9 GHz SRF cavities (one
accelerating mode and one deflecting mode cavity). These will require
single cavity feed boxes similar to that built for the first Capture
Cavity test in FY05.

2\) The module feed box and feed and end cans planned for fabrication in
FY06 should be adequate to support a four module system. However there
will need to be some modifications when four modules are installed.

3\) Part of the development of SRF infrastructure at Fermilab will be
development of Horizontal and Vertical Test Dewars. These will be
located at Meson Hall and connected to the cryogenic system.
Construction and commissioning of this system in early FY06 will be
critical for first cavity tests and preparation for module string
assembly. Cryogenic support of the test dewar will be similar to that
needed for the CapCav test in FY05 and will use much of the same
equipment.

4\) Provide CW for the proton and CW area. Additional modifications to
the feed box and feed end can will needed to support at 1.8K.

5\) For the very long term an upgrade of the injector, similar to that
that has just taken place at DESY for TTFII, has been proposed. This
upgrade would incorporate an 8 cavity TESLA module followed by a 4
cavity 3.9 GHz module as the main accelerating elements and linearizing
of the injector beam. This installation would require module feed and
end caps like those built for the 1^st^ TESLA module and/or bypass lines
to connect to the module string.

![](media/image16.wmf){width="6.0in" height="3.932638888888889in"}

Figure 10.3 Meson Enclosure Map and Present Cryogenic Transfer Line
Location

##### [Meson Area]{.underline}

The Meson beam line enclosures are shown in Figure 10.3. Currently Meson
enclosure is used for Meson Test Beam Facility (MTBF) and E907. The MTBF
is located in the M~Test~ beam line and E907 in the M~Center~ beam line.
MTBF enables experimenters who are planning experiments to test their
detectors in an active beam line and also permits detectors for other
types of research (cosmic rays, etc.) to be calibrated. E907 --The Main
Injector Particle Production (MIPP) Experiment will measure the
production of particles by the 120 GeV Main Injector proton beam for the
NuMI project targeting.

###### [Cryogenics]{.underline}

Cryogenic Test Facility (CTF), formerly the Meson Central Cryogenics
(MCC), located on the west side of the Meson beam line, can provide
cryogenics for a cryomodule test. CTF houses three (3) Tevatron
satellite refrigerators capable of producing a total of 1,500 W at 4.5K.
Cryogenic transfer line from the CTF is available in M02, M03 and M04
enclosures, formerly servicing superconducting bending magnets in
various portions of the East, Center and West beam lines. This cryogenic
system can be modified to support test operation through Phase 2 (Table
2.) Emphasis will be placed on establishing 4.5K helium and LN~2~ from
the CTF to the Meson Detector Building (MDB) for use in a single
cryomodule test utilizing a vacuum pumping system to achieve super fluid
helium. For Phase 2, a new cryogenic plant is required. Design,
construction, installation and commissioning of a new refrigerator will
require a minimum of two years from the point the contract is let.

In order to satisfy a remote super fluid helium load, the CTF
refrigerators will be operating in a liquefier mode. Operation in this
mode is inherently less reliable. It is more demanding on expander and
heat exchanger performance. Helium impurity degrades the expander and
heat exchanger performance, thus is detrimental to the reliability and
capacity of the system.

The transfer line and header connections to the refrigeration system
have been removed in order to perform cryogenic testing within CTF while
maintaining the Meson enclosures ODH Class 0. In order to reactivate the
transfer line, a new bayonet would have to be designed and built. There
is a known design flaw in some of the expansion cans used in the Meson
transfer line system. Prior to reactivating the transfer line, all
expansion cans of this type would need to be checked and repaired.
Transfer line, helium and nitrogen suction header extensions currently
leading to M02 and M03 will be isolated from the rest of the tunnel
system.

The transfer line in M~East~ will need to be extended about 300' from
ME4 to MDB. An appropriate transfer line expansion box will need to be
installed in the extension. The existing ME4 bayonet would be moved to
the MDB. The helium and nitrogen suction headers will need to be
extended by the same distance. When this work is completed, it will
enable 4.5K helium and 80K nitrogen to be delivered to the MDB.

Part of the 4.5K stream will be used in the production of superfluid
helium. The remainder of the 4.5K flow will be used to satisfy 5-8K heat
shield loads in the cryomodules and to maintain stability in the CTF/MDB
cryogenic transfer line. For convenience, the 40-80K shield loads in the
cryomodules will be cooled using 80K LN~2~. From this point, cryogens
can be distributed to SRF test area(s).

Distribution of cryogens within a test cave will require a bayonet can,
transfer line, feed can and end cap. Low pressure helium from the
cryomodule will be warmed to room temperature in a header leading to the
vacuum pumping system. It is imperative that the subatmospheric portion
of the system remains leak tight for reliable cryogenic system
operation. The vacuum pumping system requires an oil removal system to
ensure the prevention of oil migration. Care will need to be taken to
ensure that inherent vibration of the positive displacement vacuum pumps
will be isolated in order to not impact SRF performance.

The control system used at MCC during the last Fixed Target run was
removed for a cryogenic controls upgrade at CDF. Since then, new
controls have been installed and the system is now operational. The
facility is currently being operated for various Tevatron cold
compressor tests related to Collider Run II maintenance and reliability.
Future test plans include a versatile test cryostat to investigate
hydrodynamic and thermal properties of single and two phase He I and He
II. To perform tests in He II, a small vacuum pumping system has been
installed capable of cooling loads of about 10 watts down to 1.8 K.

A new local distributed cryogenic controls system is required to operate
the cryogenic distribution and vacuum pumping systems. This controls
system must be integrated to the existing CTF refrigerator controls
system. Cryogenic instrumentation required for the distribution, vacuum
pumping and cryomodule systems will feed into this controls system.

[Heat Load]{.underline}

Heat load of a single 9 cell TESLA cryomodule with a quadrupole at E =
23.4 MV/m, Q = 1x 10^10^ and 5 Hz repetition rate is presented in the
Table 10.1 below.

It is desirable to operate the TESLA cryomodules with a gradient of 35
MV/m in the SMTF. This adds considerably to the dynamic heat load. A
summary of a first pass estimated heat load at the three temperature
levels for Phase 0, 1, 2 and 3 are given in Table 10.2. Cavity RF loads
were scaled from the TESLA Technical Design Report by

![](media/image17.wmf)

Table 10.1 TESLA 8 Cavity Cryomodule Heat Load Estimate (courtesy S.
Wolff)

the cavity Q, RF pulse length and square of the gradient ratios. TESLA
TDR and A0 operating experience is used for the static heat load
estimates. Further detailed understanding of other dynamic loads within
the cryomodule is warranted. For the purpose of this study, an
uncertainty factor of 1.3 is used to compensate unknown loads. The loads
presented in Table 10.2 define the applicability of CTF as Phase 0 and 1
at a 5 Hz rep rate and Phase 2 at a 1 Hz rep rate. A new cryogenic
system is required to support Phase 2 with injector at 5 Hz and Phase 3,
as represented by the dotted line.

Table 10.2 Phased SMTF Heat Load Estimates

![](media/image18.wmf){width="5.938194444444444in"
height="2.9256944444444444in"}

11\. Generic Accelerator Physics

This section describes three separate efforts that we expect will take
advantage of the SMTF. We anticipate that as questions arise from the
R&D progress of the SMTF collaboration we will use the facility to
understand and answer them. Three areas of ongoing research which are
related to the SMTF mission are described below. This research will
provide a training ground for future accelerator physicists and
engineers.

a\. Potential applications of an electron beam at SMTF: R&D for ILC and
advanced accelerator physics

The availability of a facility providing electron beam with energies
ranging from 40-50 MeV (injector phase A) up to 1 GeV (final stage of
SMTF) will foster an extensive accelerator physics program.

In the context of ILC and current linac-based light source proposals, an
electron beam (with possible high average current), could be used to
characterize the superconducting cavities and module: from measuring the
accelerating gradient of individual cavities to studying their intricate
beam dynamics properties (focusing properties, high order mode wake
field excitations, short range wakefield study, etc...). The facility
could also test the concept of flat beam at higher energy than the
experiment being done at 16 MeV at FNPL. Such an experiment, if as
successful as predicted[^19], could have significant impact on the
design of the electron damping ring. The flat beam transform, installed
downstream of one accelerator module, could also be viewed as a full
scale demonstration of LUX flat beam generation scheme[^20]. Finally a 1
GeV electron beam facility will provide, after optimization, beam
parameters (normalized emittance, bunch length) identical to those that
would be achieved at 5 GeV by the ILC injector. Thus the facility could
serve as a test stand for optimizing the injector beam parameters and
developing the proper beam instrumentation needed to diagnose the beam.

At a latter stage, our foreseen design does not preclude, for
experimental purpose, the exchange of the rf-gun with a polarized gun
(either RF or DC) for production of polarized electron beam.

At energies above 500 MeV, the electron beam can also be used to produce
positrons (by impinging a tungsten target for instance), a lot of beam
dynamics aspects of the positron source, especially the capture section
including the adiabatic matching device, could be tested and optimized
at SMTF.

Finally if the accelerator is available a priori to the construction of
the European X-ray FEL, there are aspects of the X-FEL design that could
be tested at SMTF (for instance the rf-gun in the XFEL is operated at
higher gradient that in TTF VUV FEL and this has impact on the distance
between the rf-gun and 1^st^ accelerating module location)

High energy electron beam will also provide a tool for testing new ideas
or concepts, for instance flat beam propagated very close to a
grating[^21], or between two gratings can provide intense pulses via the
Smith-Purcell effect, such an idea is presently thought to be the path
toward ultra-short wavelength compact FELs utilizing the so-called image
charge undulator[^22]. In addition the advanced accelerator physics
program currently pursued at FNPL (plasma-wake field acceleration,
laser-based acceleration, etc...) could be extended (for instance at 100
MeV the vacuum laser-based acceleration is possible without the use of a
medium to slow the laser phase velocity). We expect R&D on
instrumentation to be a large activity at SMTF, for instance the recent
use of electro-optical sampling in beam diagnostics has open new
possibilities for measuring beam distribution with 100 femtosecond
resolution[^23]. This technique could be extended at SMTF. On another
hand beam halo detectors being developed for high intensity proton linac
could be tested with electron beam. There is finally a new class of
accelerator-based astrophysics experiments being considered[^24], this
type of experiments could also be envisioned at SMTF. We should finally
mention that there is a strong synergy between advanced accelerator
physics and optical techniques, the SMTF collaboration should therefore
undertake the development of a laser laboratory (operating and upgrading
the photocathode drive laser and also a ultra-short infrared laser
capable of providing 100 fs pulses).

As briefly outlined in this Section, we expect the opportunity of having
a high energy electron beam to drive an extensive program of accelerator
and beam physics. This sort of program and operation of the SMTF with
beam is important for training of young accelerator scientists and
engineers.

b\. SRF Materials R&D at SMTF

The SMTF activity will also include materials R&D to support the
gradient and Q goals of SMTF, as well as to pursue ultimate gradients
and lower cost of SRF linear accelerators. There are many material R&D
topics worthy of further investment. The following list, without
claiming to be exhaustive, identifies the most important among them.
There are also several superconducting materials that can be used for
SRF cavities. It is clear, however, that niobium will most likely be the
prime candidate material for a large-scale linear collider. Therefore
the following topics are mostly related to niobium.

1.  Improving the understanding of the effect of the cavity processing
    steps such as polishing and baking on the chemical surface
    composition and its impact on the RF surface resistance at high
    fields;

2.  Understanding and measuring the critical RF field;

3.  Measuring the superconductor property profile (e.g. gap energy)
    across the RF field penetration layer;

4.  Improving the understanding of the dynamics of RF vortex penetration
    into the superconductor, with particular emphasis of the effects of
    grain boundaries (and grain boundary chemistry) and surface
    topology;

5.  Understanding and improving the high electric field breakdown and
    field emission thresholds;

6.  Understand and improve the basic material properties, such as
    thermal conductivity and Kapitza interface resistance;

7.  Surface analysis measurements with surface analytical tools such as,
    SEM, SAM, XPS, and SIMS as warranted to improve understanding of the
    composition and the physics of RF penetration layer.

8.  Continue to develop Cu-Nb composite cavity fabrication technologies,
    such as based on co-extrusion or thin films, and the associated
    knowledge of the material properties (such as the mechanical
    properties);

All national laboratories and universities participating in this
proposal conduct some basic SRF along with material R&D. The
collaborative activities of SMTF will be an excellent forum for
dissemination of ideas and results. Most of the listed issues are being
addressed Extensive surface analysis is being carried out at JLab
Cornell and to further our understanding of the physics of the RF
penetration depth (item 7). RF critical field measurements are being
continued as for example on niobium at 11.4 GHz by a SNS/SLAC/JLab
collaboration under R. Campisi (item 2 in list). Other examples are the
plasma sputtering efforts at JLab/Cornell collaboration (item 7) or the
effort at MSU to measure the thermal properties of high purity niobium
for SRF (item 6). Fermilab has just recently launched two potentially
promising collaborations with the UW and NU. The collaboration with the
UW aims to improve the understanding of the dynamics of RF vortex
penetration into the superconductor, item 2 in the above list. The
collaboration with NU was established to investigate the chemical
properties of the high purity niobium used in the cavity fabrication
with 3D atomic probe microcopy (3DAP). This activity therefore addresses
item 1 in the above list. 3DAP will also be used to investigate field
emission in SRF cavities (item 5), a collaboration between NU and ANL.
Other material related activities that practically all SRF laboratories
engage in are (electron-) microscopy, surface roughness analysis, RRR
measurements and eddy current scanning. Fermilab, for instance, is
developing a host cavity to measure the properties of small samples
prepared by different methods. The aim is to rapidly measure a large
number of samples prepared by the same method to obtain good statistics.

In short, the SMTF effort will bring together a large number of world
leading experts to address basic issues in SRF performance.

12\. Cost and Schedule

In this section we present the cost and schedule for the SMTF.

13\. SMTF Organization

The collaboration is in process of forming an SMTF organization. The
collaboration will be led by two co-spokespersons, who will chair an
Institutional Board, which comprises of one representative per
collaborating institutions and the project leaders. The institutional
board members have been selected by the collaborating institutes. A
Technical Advisory Board will be appointed by the institutional board.
The collaboration will interact with the Fermilab management through the
Associate Director for Accelerator and Technologies. Fermilab has an
internal SMTF organization that has the responsibilities of the
infrastructure, day-to-day operation and safety.

![](media/image19.png){width="5.995833333333334in"
height="4.490972222222222in"}

[Fermilab SMTF Organization:]{.underline}

Fermilab has a stated strategy of pursuing International Linear Collider
and Proton Driver R&D programs in parallel. Because the two programs are
developing implementations based on SRF, the opportunity exists for
effective utilization of Fermilab resources through sharing of
infrastructure and people. The SMTF will facilitate integration, and
become a significant component, of these programs. Because multiple
organizations are involved, both within and outside Fermilab,
coordination of SRF-based activities from within the Directorate is
desirable. The goal is a unified approach that maximizes the
effectiveness of available resources.

The Accelerator (AD) and Technical (TD) Divisions are providing, and
will continue to provide, the bulk of Fermilab resources in support of
the ILC and PD programs. Support from the Particle Physics (PPD) and
Computing (CD) Divisions will be encouraged and welcomed to the extent
practical. Presently program leaders for both ILC and PD reside in TD.
However, as the bulk of Fermilab's accelerator physics and engineering
expertise continues to reside in the AD it is important to integrate
this effort, as the Run II Upgrade effort starts to roll off, while
minimizing the potential impediments imposed by division boundaries. To
this end it is proposed to organize and manage the ILC, PD, and SMTF
efforts as an integrated activity.

[Goals and Responsibilities]{.underline}

The organizational/management goal is to provide coordination and
integration of the three SRF based activities at Fermilab: ILC, PD, and
SMTF. A Fermilab organization is proposed in which the Associate
Director for Accelerators (ADA) retains responsibility for integration
and coordination of Fermilab's SRF based programs: ILC R&D, Proton
Driver R&D, and SMTF. Figure 13.1 shows an organization to achieve these
aims. This organization represents an integrated line management
structure. In interpreting the organization chart "SMTF" refers to the
facility in which SRF hardware is tested, ILC refers to the Fermilab
based component of the International Linear Collider R&D program,
including both SRF and non-SRF components, and "PD" refers to the
Fermilab based Proton Driver R&D program, again including both SRF and
non-SRF components.

While each programs draws support from across division boundaries, each
also has a host division which holds overall responsibility for
planning, execution, and reporting against the agreed upon scope of
work. The establishment of a host division is intended to enhance, not
impede, the integration of effort across division boundaries. TD
currently is the host division for ILC and PD, and will remain so for
the immediately foreseeable future. AD will assume the responsibility as
host division to the SMTF.

The primary mechanism for coordinating these activities will by a
Fermilab SRF Steering Committee consisting of the ADA, the program
leaders, the program engineers, the SMTF facilities manager, and the AD
and TD heads. The ADA, as chair of the steering committee, and his
deputy, hold line management responsibility for all aspects of the SRF
based program at Fermilab.

[Figure 13.1: Fermilab SRF Organization Chart]{.underline}

a\. International Collaboration on SMTF

The following sections are either summary of our discussions with the
institutes and/or have been provided by the institutional
representatives.

INFN

The SMTF management is in discussion with Carlo Pagani (Milano) and
Giorgio Bellettini (Pisa) on the possible contribution of INFN to the
ILC component of SMTF. More general discussions have taken place with
Sergio Bertolucci of Frascati. The initial discussions have identified
three possible areas of collaboration; the cryomodule

cold mass, a \"Chechia\" horizontal test facility, and the Low-Level RF.

The primary area of initial interest is the cryomodule cold mass. INFN
has been asked to be the lead institution for producing the cold mass.
INFN, through the work led by Carlo Pagani and collaborators, are the
world\'s experts in the design and fabrication of the Tesla

Cryomodule used at the DESY Tesla Test Facility. The cold mass consists
of all components (structural support backbone and other cryogenic
piping, superinsulation, mu-metal, instrumentation etc.) surrounding the
dressed cavities including the vacuum vessel. INFN is being asked to
share the costs of the materials and engineering with SMTF and to
provide the engineering designs. Improvements to the existing design and
on where the cold mass will be fabricated are also being discussed.
Fabrication may take place in European and US industries. Fermilab will
provide engineering assistance

to INFN for the modifications to the design of the cold mass.

The detector system and the programmable logic to be designed for real
time beam amplitude and phase control by the Low-Level RF seem well
tuned to the expertise of the CDF-Pisa group. A possible contribution of
that group to this project is being discussed with Giorgio Bellettini
and with Luciano Ristori.

KEK

KEK will collaborate with SMTF in several areas. At present the details
of the collaboration are still under discussion and still being worked
out. Nevertheless, there is one primary area of interest being discussed
that both KEK and SMTF find of mutual benefit. KEK will provide SMTF
with up to eight (4 in FY05 and 4 in FY06) SRF cavities fabricated in
Japan. These \"bare\" cavities will likely be of the \"high gradient\"
design. The dressing of the cavities is under discussion. SMTF will
assemble the cavities into a string, and insert them into the cold mass
and cryomodule and test with beam.

The TESLA Collaboration

A close association with the Tesla Collaboration is critical to the
success of the SMTF. They have agreed to help SMTF with a very open and
collaborative spirit. They are providing designs, along with numerous
engineering discussions, software, and a cryomodule for testing at SMTF.
The makup of SMTF includes members from the Tesla Collaboration as well
as DESY and vice-versa. Joint meetings are underway to discuss the roles
and relationship of the two organizations.

DESY and SMTF

It is recognized that DESY is a key player in successful technology
transfer to SMTF. To this end DESY has offered to provide Fermilab (a
long term TESLA collaborator) with a Tesla module in the time frame
2006/2007. The integration of this module into the SMTF plan is
discussed elsewhere in this proposal.

The DESY management supports the SMTF effort and recognizes the
importance of free and open exchange and use of each other's facilities
and exchange of personnel. As well, DESY recognizes its essential role
toward fostering the start up of regional facilities such as SMTF.

It is expected that as the structure of the ILC GDI is established that
a clear picture of the formal international organization of and
interplay between the different test facilities will develop. At this
juncture DESY believes it is best to continue to collaborate within the
framework of the present agreements which have been successful now for
the many years of the TESLA collaboration, and to wait for that
international structure to evolve in order to formulate the formal
structure.

14. Summary

The SMTF represents a major new initiative by Fermilab and its national
and international collaborators to advance SRF accelerator technology.
The SMTF collaboration will fabricate and process SRF accelerating
cavities and SRF components in collaboration with industry. The facility
would then be used to assemble the cavities into cryomodules
(accelerator sub-units), as well as test, and validate the designs with
an electron beam . The R&D performed at SMTF will be of value to several
planned accelerator projects: The International Linear Collider; Proton
Driver; Rare Isotope Accelerator and 4^th^ Generation Light Sources. .

[^1]: See for details
    [http//:nicadd.niu.edu/fnpl](http://nicadd.niu.edu/fnpl/)

[^2]: V. Ayvazyan, et al, Phys. Rev. Lett. **88**, 104802 (2002)

[^3]: N. Solyak, et al., in *Proceedings of the 2003 Particle
    Accelerator Conference, Portland OR* , IEEE Publishing, Piscataway,
    New Jersey, p. 1213 (2003)

[^4]: L. Bellantoni et al, in *Proceedings of the 2001 Particle
    Accelerator Conference*, Chicago IL, IEEE Publishing, Piscataway,
    New Jersey, p. 1077 (2001)

[^5]: K. Flöttmann and P. Piot, in *Proceedings of the 2002 European
    Particle Accelerator Conference,* Paris, IOP publishing, p. 1798
    (2002)

[^6]: Y.-E Sun, P. Piot, *et al*., Phys. Rev. ST Accel. & Beam **7**,
    123501 (2004)

[^7]: D. Edwards *et al*., in proceedings of the XX international Linac
    Conference, Monterey CA, (SLAC, Stanford 2000), p.122 (2000)

[^8]: R. Tikhoplav *et al*., in proceedings of the XXII international
    Linac Conference, Lübeck, Germany (2004) preprint available at
    <http://bel.gsi.de/linac2004/PAPERS/MOP46.pdf>

[^9]: M. Thompson *et al*., Status of the UCLA/NICADD plasma density
    transition trapping experiment, Conf. Proceeding of the 11^th^
    Advanced accelerator concept workshop AIP Conf. Proc. **737**, p 440
    (2004)

[^10]: R. Tikhoplav, *et al*., in *Proceedings of the 2002 European
    Particle Accelerator Conference,* Paris, IOP publishing, p. 984
    (2002)

[^11]: G. Gollin, expression of interest available
    <http://www.hep.uiuc.edu/home/g-gollin/Linear_collider/A0_committee_presentation.pdf>

[^12]: M. Fitch, et al, Phys. Rev. Lett. **87**, 034801 (2001)

[^13]: LUX informations are available at
    [http://lux.lbl.gov](http://lux.lbl.gov/). The idea of generating
    ultra-short pulse based on the use of a deflecting cavity was
    introduced in A. Zholents et, Nucl. Instr. Meth. **A425**, p. 385
    (1999).

[^14]: See for instance K. Flöttmann, T. Limberg and P. Piot, DESY
    report TESLA-FEL-01-06 (2001)

[^15]: P. Piot, and W. Decking, A modified post damping ring bunch
    compressor beamline for the TESLA linear collider, FNAL TM-2235
    (March 2004)

[^16]: A new laser oscillator has been procured by NIU and the upgrade
    of the laser will happen in spring 2005 following the proposal by N.
    Barov, J. Li, and R. Tikhoplav, Beams Document 1342-v2 (August 2004)
    (document available at
    <http://beamdocs.fnal.gov/DocDB/0013/001342/002/oscillator_final.pdf>)

[^17]: K. Flöttmann, P. Piot, M. Ferrario, T. Limberg and B. Grygorian,
    in *Proceedings of the 2001 Particle Accelerator Conference,*
    Chicago IL, p. 2236 (2001)

[^18]: B. Dwersteg, K. Floettmann, J. Sekutovicz, and Ch. Stolzenburg,
    *Nucl. Instr. Meth*. **A393**, p. 93 (1997)

[^19]: P.Piot, presentation at the 1^st^ ILC workshop, slides available
    at
    <http://lcdev.kek.jp/ILCWS/Talks/15wg3-30-WG3-30_Electron_Discussion_Piot.pdf>
    (November 2004)

[^20]: S. Lidia, in *Proceedings of the 2004 European Particle
    Accelerator Conference,* Lucerne Switzerland, p. 476 (2004)

[^21]: K.-J. Kim and S. B. Song, *Nucl. Instr. Meth*. **A475**, p. 158
    (2001)

[^22]: Y. Zhang, Ya. Derbenev, J.R. Boyce, and R. Li., in *Proceedings
    of the 2003 Particle Accelerator Conference, Portland OR* , IEEE
    Publishing, Piscataway, New Jersey, p. 941 (2003)

[^23]: Result achieved by the SPPS collaboration at SLAC (2004)

[^24]: See for instance review by J.S.T. Ng,
    <http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-r-630-ch40.pdf>