**Discussion Document**

**\
A Crystal Collimation Experiment at the Tevatron**

***Abstract:***

*We are writing this letter to express our interest in pursuing an
experiment at Fermilab's Tevatron to measure the predicted improvement
in collimation efficiency that could be obtained by replacing amorphous
primary collimators with bent crystals. Considering the unique
possibility provided by the Tevatron Collider, and having already
established fruitful collaborative efforts on crystal characterization,
tests and use for collimation, we propose to test and confirm models of
multi-turn dynamics with crystals by exploiting channeling and newly
understood phenomena such as volume reflection. In our view, this is a
necessary first step to being able to evaluate an engineering
implementation of this technique in LHC that if proven promises an
enhanced performance of the LHC collimation system with a reduced
impedance and easier implementation for heavy-ion beam halo cleaning.
There is also an interest to crystal channeling from the ILC and Muon
Collider projects. We present the conceptual design of the system,
results obtained in preliminary beam tests, and plans for the near-term
measurements. Then minor modifications to the Tevatron needed to
implement the full crystal and beam diagnostics systems are described
along with studies proposed at a second stage based on substantial
contributions of all the parties involved. The US LHC Accelerator
Research Program (LARP) will co-ordinate and partially support the U.S.
side of the collaboration.*

Table OF COntents

[1. Introduction and Motivation 3](#introduction-and-motivation)

[2. First Studies at the Tevatron 5](#first-studies-at-the-tevatron)

[2.1 Crystal Setup 5](#crystal-setup)

[2.2 First Measurements 7](#first-measurements)

[2.3 Modifications 10](#modifications)

[3. Crystal Collimation Experiment 12](#crystal-collimation-experiment)

[3.1 Goal and Deliverables 12](#goal-and-deliverables)

[3.2 Phase I 14](#phase-i)

[3.3 Phase II 15](#phase-ii)

[4. Outlook 15](#outlook)

[4.1 Rough Estimate of Cost and Timeline
16](#rough-estimate-of-cost-and-timeline)

[Bibliography 18](#bibliography)

# Introduction and Motivation

At hadron colliders, as at any other accelerator, the creation of beam
halo is unavoidable. This happens because of beam-gas interactions,
intra-beam scattering, proton-proton, proton-antiproton or heavy-ion
collisions in the interaction points (IP), and particle diffusion due to
RF noise, ground motion and resonances excited by the accelerator magnet
nonlinearities and power supply ripple. As a result of halo interactions
with limiting apertures, hadronic and electromagnetic showers are
induced in accelerator and detector components causing numerous
deleterious effects ranging from minor to severe. An accidental beam
loss caused by an unsynchronized abort launched at an abort system
malfunction can cause catastrophic damage to the collider equipment.
Only with a very efficient beam collimation system can one reduce
uncontrolled beam losses in the machine to an allowable level \[1\].
Beam collimation is mandatory at any superconducting hadron collider to
protect components against excessive irradiation, minimize backgrounds
in the experiments, maintain operational reliability over the life of
the machine (quench stability among other tasks), and reduce the impact
of radiation on the environment.

In so-called single-stage conventional collimation the beam halo is
scraped by a collimator moved into the halo. Typically the collimator is
a 1.5 m long block of steel or other medium or high-Z material. A
certain fraction of the halo will survive, either by traversing the
length of the collimator or by scattering out of the collimator block.
Suppressing the out-scattered particles is quite difficult, so that the
typical efficiency of a single-stage collimator is of the order of 50%
for high-energy beams. A more sophisticated way to handle the
out-scattered particles is to go to a two-stage collimation system. As
shown in the left-hand panel of Fig. 1.1, a thin primary target is used
to scatter the beam out by increasing the amplitude of the betatron
oscillations of the halo particles and thereby increasing the impact
parameters on to secondary collimators during the next turns without
influencing the unscattered beam. The overall collimation efficiency of
the Tevatron two-stage collimation system is 99.9%. That is adequate for
the machine performance. At the same time, the situation at the LHC --
with its hundreds times more powerful beam - is more stringent,
requiring a higher collimation efficiency.

A crystal channeling collaboration of several groups from Europe, USA
and Russia -- which started about 15 years ago -- has recently been
stimulated by an exciting new challenge. The challenge is related to the
potential crystals provide for Phase 2 of the LHC collimation, the
recent encouraging results from the experiments at the Tevatron and the
H8 beam at the CERN SPS, and new developments in crystal techniques
including the volume reflection phenomenon. Crystals also provide
interesting possibilities for beam separation at J-PARC and beam halo
collimation at the ILC. First results are already available and tests
are planned at CERN with the H8 beam of 300-GeV electrons that bear on
the ILC.

Extremely high inter-planar electric fields from screened nuclei (a few
GV/cm) make it possible to bend and focus high-energy beams with very
short crystals \[2\]. The bent-crystal technique is well established as
a technique for extraction and handling of high energy hadron and
heavy-ion beams from accelerators. The extraction technique was
successfully demonstrated in the mid-80's through the mid-90's for up to
900 GeV beams at JINR, IHEP, CERN and Fermilab. Measurements have
demonstrated the high efficiency predicted in simulations. Recent
results from Japan for channeling with proton and electron beams are
consistent with earlier data. Bent crystals are routinely used at IHEP
to extract and form proton beams with an intensity of 10^12^ ppp and
higher. It has been shown at CERN, IHEP**,** and Fermilab that crystals
are heat- and radiation-resistant. Deflection efficiency deteriorates at
a rate of about 6% per 10^20^ p/cm^2^ \[3\].

The promise of bent crystal channeling technique for beam halo
collimation at high-energy colliders was recognized at the SSC in 1991
\[4\]. A bent crystal, serving as a primary element, coherently deflects
beam halo particles, directing them deeper into a second collimator body
compared to the case of an amorphous primary scatterer (Fig. 1.1,
right). This would substantially reduce the out-scattering probability
from the system. Moreover, the number of inelastic nuclear interactions
in the optimal crystal is typically four times lower for high-energy
proton beams compared to that in an optimal amorphous target. That
reduces radiation load to the downstream superconducting magnets by the
same factor. Preliminary measurements of channeling collimation,
performed at IHEP in 1998 for 1 to 70 GeV protons \[5\], confirmed the
basic findings and demonstrated an increase of the collimation
efficiency with energy.

![](media/image1.png){width="3.1666666666666665in"
height="2.3916666666666666in"}
![](media/image2.png){width="3.1215277777777777in" height="2.75in"}

Figure 1.1: Principle of two-stage collimation with a primary collimator
based on an amorphous target (left) and a bent crystal (right).

Based on realistic modeling, it was proposed to implement a bent crystal
in the Tevatron collimation system \[6\]. Calculations have indicated
that employing a silicon bent crystal instead of amorphous primary
collimators (targets) can improve the Tevatron collimation system
efficiency and reduce backgrounds in the CDF and D0 collider detectors:

-   by a factor of 2 with one (horizontal) target replaced, and with
    contribution from beam-gas scattering unsuppressed;

-   by a factor of 3 with one (horizontal) target replaced, and with
    contribution from beam-gas scattering suppressed;

-   by a factor of 4 to 6 for the two-plane collimation.

A crystal collimation experiment was performed at RHIC at BNL in 2003
\[7\]. Measured bent crystal channeling efficiency for gold ions was
found to be 26%. Crystal channeling worked as expected and as predicted
by simulations, once lattice functions and halo distribution were
understood. Reduction of background was not achieved because the lattice
was not optimal in the area of collimator resulting in an angular spread
at the crystal which was too high.

Parenthetically, this recent work at RHIC and later at FNAL uncovered
the importance of the long-neglected coherent crystal effect predicted
at Tomsk two decades ago, volume reflection \[8\]. Conventional
channeling and volume reflection are illustrated in Fig. 1.2. Contrary
to ordinary channeling, which is extremely sensitive to beam-crystal
alignment (10-μrad level in the Tevatron), volume reflection has a much
higher angular acceptance. Therefore it seems to be very promising as a
collimation tool for high-energy beams. The studies have helped to spark
interest in the volume reflection process including a fast track
investigation in the H8 beam at the CERN SPS in the fall of 2006. That
precision investigation has produced a spectacular confirmation of
volume reflection with 97% efficiency \[9\] and also developed tools to
characterize crystals that could potentially serve as LHC collimators.

![](media/image3.png){width="5.666666666666667in"
height="3.058333333333333in"}

Figure 1.2: Schematics of beam channeling and volume reflection.

# First Studies at the Tevatron

## Crystal Setup

In the fall of 2004, the modified BNL assembly with a 5-mm thick silicon
crystal was installed in the Tevatron in the dog-leg of the E0 straight
section downstream of the horizontal 5-mm thick tungsten primary
collimator D49 (Fig. 2.1). The primary collimator and crystal could be
alternatively inserted into the beam halo. The phase advance with
respect to the secondary collimators was similar in both cases. A
scattered baseline beam or a beam deflected by the crystal was
intercepted by a 1.5-m long steel secondary collimator E03H 23.8 meters
downstream. At E0 the proton helical orbit is on the inside of the
accelerator central orbit. Fig. 2.1 is a schematic of the location,
while Fig. 2.2 shows the crystal assembly.

![](media/image4.png){width="5.249305555555556in"
height="3.2402777777777776in"}

Figure 2.1: Schematic of the experimental setup at E0.

![](media/image5.jpeg){width="3.25in" height="2.214583333333333in"}

Figure 2.2: E0 crystal collimator assembly (left) and O-shaped crystal
in holder (right).

The crystal was mounted in a high vacuum goniometer. It rotated around a
vertical axis with a pivot point about 8 cm from the beam and deflected
the halo in the horizontal direction. The crystal orientation could be
monitored with a laser system. The device moved in and out of the
accelerator beam pipe in the horizontal plane. The crystal was a
so-called \"O\" crystal of silicon with the bend in a (110) plane. It
had a miscut angle of 0.465 mrad arranged so that there was not a
possibility of partial deflections for particles near the crystal face.
The \"O\" geometry pioneered at PNPI produces a bend in the small leg of
the \"O\" by compressing the long leg. The length of the crystal along
the beam was 5 mm. The long leg of the \"O\" was 45 mm. The bending
angle was approximately 0.44 mrad. The crystal deflected the beam toward
the inside of the ring.

The principal detector used for this investigation was an ion chamber
beam loss monitor (LE033) behind the E03 collimator (labeled E03H in
Fig. 2.1). The LE033 signal was generated by scraped or channeled halo
showering in the E03 collimator. The signal was reduced significantly
when the collimator was withdrawn. For example the collimator
out/collimator in ratio when the crystal was aligned for channeling was
\< 0.01. A standard PIN diode (LE0PIN) was also available about 25 cm
downstream of the crystal. It was at an angle of about 45 degrees to the
beam so that it was detecting mostly low-energy secondaries from
interactions in the crystal. Removing the crystal from the beam halo
caused the LE0PIN signal to disappear. Detectors like C:LOSTP at the CDF
collider detector were used to monitor proton losses for different
collimation arrangements at E0. Since the crystal was 5-mm long, the
interaction probability per pass was only 1.6%. Thus, when the 1.5-m
collimator was moved in closer to the beam than the crystal, the count
rate in LE033 have been sixty times higher.

## First Measurements

Beam studies first at 150 and then at 980 GeV were conducted in the
Tevatron in the summer and fall of 2005. These were a series of 2-hour
long End-of-Store Studies (EOS). The crystal was aligned in the halo by
varying its angle in steps of several μrad. Typically the crystal angle
was scanned over 2000 μrad in forty-five minutes. Several points were
taken for each angular setting.

Collimators E03H and F172H were used to intercept a channeled beam. All
other collimators were pulled out, with the exception of the A48V
tertiary one used for kicker prefire protection. At any angle there were
statistical fluctuations due to slight beam motions in the Tevatron at a
minute by minute level. Fig. 2.3 shows the LE033 readings behind
collimator E03 as a function of the crystal angle for a typical scan.
The crystal angle scale has been set to 0 μrad for the situation where
the front end of the crystal is aligned.

![](media/image7.jpeg){width="4.916666666666667in"
height="3.761111111111111in"}

Figure 2.3: Crystal angle scan. The CATCH simulation results are shown
in red.

Characteristically the crystal was at 5.5 σ~b~ from the beam while the
collimator was at 6 σ~b~ (σ~b~, the horizontal spread of the beam, was
0.45 mm). A channeling dip is present at 0 μrad with a width of 22 ± 4
μrad (rms). The width of the channeling dip is a convolution of the beam
divergence, the channeling critical angle, and multipass channeling
effects. The width of this distribution can be compared to the 32 μrad
width (rms) observed in the E853 crystal extraction experiment at the
Tevatron for a collider mode beam angular divergence at the crystal of
18 μrad. It is difficult to do a deconvolution of the crystal angular
scan to get the critical angle. However, the distribution is consistent
with the beam divergence and the 5 μrad channeling critical angle at 980
GeV. At the bottom of the dip the LE033 signal is 22% of the signal at a
random angular setting. This depth is a measure of the channeling
efficiency and gives a channeling efficiency of η~c~ = 78 ± 12%
including the effects of multiple passes.

A shoulder extends 460 ± 20 μrad to the right of the channeling dip. A
similar feature was observed for the first time at RHIC. This shoulder
width is equal to the magnitude of the crystal bend. The shoulder is a
coherent crystal effect acting over the whole arc of the crystal bend. A
typical volume reflection away from the convex side of the crystal is on
the order of the critical angle. It is a coherent process so over
several passes through the crystal it can grow to a deflection several
times the critical angle. Like channeling it will diminish nuclear
interactions and thereby decrease the LE033 rate. The whole-arc
efficiency, η~r~, was 52 ± 12%. The results of Biryukov's CATCH
simulation for the conditions in the Tevatron are shown in the plot.
Note that there are no free parameters in this simulation except average
counting rate. The angular distribution of particles interacting with or
channeling in the crystal was measured by plotting the LE033 count rate
as the E03 collimator was withdrawn further from the beam. Note that the
LE033 signal is an integral of the flux as a function of radial position
along the front face of the collimator.

The central purpose of the Tevatron study has been to demonstrate and
study effective crystal collimation to reduce halo at the collider
detectors. Both of the large detectors at Fermilab have halo monitors to
monitor these losses continuously. During the crystal collimation
studies, the CDF LOSTP halo monitor was recorded for most of the runs.
Fig. 2.4 shows a comparison of crystal collimation with the crystal
aligned for channeling collimation and for the case for conventional
collimation with a thin tungsten target at D49. For CDF losses, the
crystal case goes down to a rate about half the rate with the
conventional D49 W target. In the crystal case, the nuclear interaction
rate in it, proportional to the PIN diode readings, is substantially
lower compared to that in the tungsten target.

![](media/image8.wmf){width="3.1666666666666665in" height="2.125in"}

![](media/image9.wmf){width="3.1666666666666665in"
height="2.1194444444444445in"}

Figure 2.4: E03H collimator effect on halo at CDF for D49 amorphous
target (left) and using the bent crystal. (right). Dark blue symbols are
LE033 rates, magenta symbols are PIN diode readings, and cyan symbols
are C:LOSTP beam loss rates at CDF.

**To reiterate, when using the crystal, the secondary collimator E03
achieved almost a factor of 2 better reduction of CDF losses a half a
ring or three kilometers downstream (in agreement with modeling)!
Moreover, the secondary collimator could remain further (1 mm or so)
from the beam thus reducing impedance, and the nuclear interaction rate
in the crystal was 2 to 3 lower compared to the amorphous target,
reducing proportionally irradiation of the downstream components.**

## Modifications

The first crystal collimation test system collimates only in the
horizontal plane. A comprehensive system would also collimate in the
vertical plane as well as in dispersion for off-momentum partricles.
These results are multiplicative, so the halo scraping could be improved
by up to a factor of eight. The original modeling indicated that in an
ideal Tevatron lattice, an order of magnitude reduction might be
achieved. Thus, the present incomplete and rudimentary system appears to
be well on the way to fulfilling the potential of crystal collimation.
We aim at the full system in Phase II of this proposal.

It turned out that the parameters of the BNL's crystal used in the first
studies are not optimal for the Tevatron conditions. Express simulations
by V. Biryukov, have shown that the collimation efficiency can be
noticeably improved by replacing the original 5-mm long crystal with a
shorter one which has a smaller bending angle (Fig. 2.5). Of course, the
optimal parameters depend on details of the lattice, collimation system
configuration and beam loss region layout, but the trends shown in the
Fig. 2.5, convinced us to replace the original crystal with a new
shorter one. Moreover, we also wanted to investigate a new technology
developed to improve crystal performance.

![](media/image10.png){width="4.751388888888889in" height="3.3375in"}

Figure 2.5: Estimated beam loss reduction in Tevatron as a function of
crystal length for two bending angles as simulated with CATCH (courtesy
V. Biryukov).

In 2006, the original O-shaped crystal was replaced with a new custom
crystal based on a novel strip technology. It was designed, fabricated,
mechanically bent and characterized in a collaboration between IHEP
(Protvino) and the University of Ferrara-INFN. The chemically etched
crystal is 3-mm long (along the beam) with a 0.15-mrad bending angle
(Fig. 2.6). The new crystal was installed in the Tevatron in late 2006.

![](media/image11.jpeg){width="4.0in" height="3.0in"}

Figure 2.6: Strip crystal prepared by IHEP and INFN and installed in
Tevatron in late 2006.

A team of experts from IHEP, CERN, INFN and KEK came to Fermilab in
February 2007 to perform measurements with the new crystal. In a series
of EOS studies, the entire angular range has been scanned at 2 μrad
steps. No channeling was detected. It was then found that there was a
problem with the alignment of the crystal.  It was misaligned by
\~14mrad.   The crystal was realigned and scans continued on May 26,
2007.

![](media/image12.wmf){width="5.166666666666667in"
height="3.4743055555555555in"}

Figure 2.7: Angle scan with the new strip crystal.

The data which looked like channeling was demonstrated with the new
crystal (Fig. 2.7). But the size of the volume reflected region should
be proportional to the bend angle of the crystal (150μrad).  The data
showed \~ 320μrad which is too large. Therefore, an additional period on
July 9 was requested to produce a finer 1-μrad scan of this region.
However, channeling could not be observed at all. During the fall 2007
shutdown, the laser scans in the tunnel have revealed that there is
unacceptably large wobbling of the new crystal holder, which is much
heavier than the original one. As a result, the positioning of the
crystal with respect to the beam is extremely unstable, and results of
the angle scans are irreproducible. The current consensus is that the
mechanics (goniometer) needs to be replaced.

# Crystal Collimation Experiment

## Goal and Deliverables

Crystals are an interesting advanced technology for Phase 2 of LHC
collimation. To evaluate their benefits in detail the following
information is required:

-   Crystal parameters for the highest efficiency for channeling and
    volume reflection at both injection (450 GeV) and top (7 TeV) proton
    energies.

-   Probability spectrum of proton deflections at 0.45 to 7 TeV for all
    physics processes down to a 10^-5^ level.

-   Damage limit of crystals for instantaneous shock beam impact at \~15
    MJ/mm^2^.

-   Damage limit of crystals for integrated dose at \~5×10^16^ p/year at
    7 TeV.

-   Handling of crystals during normal operation at high-power impact.

-   Number, opening (impedance) and locations of absorbers for extracted
    and scattered beam.

-   Sensitivity to beam angle and angular spread in the TeV region.

-   Requirements for alignment and operational set-up (tolerances, time,
    etc.).

Aiming at the high-performance collimation vital for the LHC,
considering the unique possibility provided by the Tevatron collider
(before its shutdown for collider physics), and having already
established fruitful collaborative efforts on crystal characterization,
tests and use for collimation, we propose to conduct crucial studies in
the time frame required by the LHC plans. The primary goal would be to
address the issues listed above in the next two or three years. The
directions would include:

-   Beam tests in the CERN SPS extracted beams including measurements
    with 400-GeV protons, 200 GeV/A ions, and 30-GeV electrons and
    positrons.

-   Beam tests as well as post-irradiation tests employing the Tevatron
    beam abort line to study damage limits of crystals; these
    high-priority studies would use mechanical, optical tests and SPS
    beams.

-   Design and fabrication of new crystals characterized mechanically,
    optically and with beams.

-   Studies of novel technologies to improve efficiency (multi-strip,
    quasi-mosaic, etc.).

-   Further development of the crystal-related theoretical models and
    simulation tools for refined modeling of the channeling and volume
    reflection effects in the crystals and particle tracking in
    realistic multi-component collimation systems and collider lattices;
    full-scale modeling of the system performance in the Tevatron and
    LHC realms.

-   Development of beam and alignment instrumentation -- including
    single-particle tracking - adequate to crystal-based collimation,
    and the test of the instrumentation at the Tevatron.

-   Demonstration in the Tevatron of single and multi-crystal volume
    reflection, and of a two-plane crystal collimation.

-   Full-scale crystal collimation experiment at the Tevatron with up to
    three crystals, two for betatron cleaning and one for momentum, with
    beam diagnostics as above.

-   Possible crystal collimation experiment in the SPS ring.

-   Preliminary tests of crystals at U70 at IHEP (Protvino).

The following near-term action items are important for understanding in
a timely manner the potential of channeling collimation at the LHC:

1.  Experiments should be conducted to provide information about the
    possible deformation of the crystal or crystal holder during a
    vacuum baking process. It would be good to go up to 200 degrees C.

2.  IHEP/CERN/INFN will provide Fermilab with the crystal that was
    characterized in the H8 experiment at CERN.

3.  Consider and design a crystal damage experiment where crystals and
    instrumentation for assessing dose rates could be placed in the
    Tevatron abort line. Once enough beam is integrated on one crystal,
    it should be moved back to CERN for H8 beam line characterization.
    Ideally several crystals should be studied at once so one could be
    removed early.

4.  Consider and design a test at the end of the Tevatron experimental
    collider run (2009) for crystal collimation studies. The test would
    be 2 to 4 weeks long and would be used to demonstrate two-plane
    crystal collimation. This proposal will need new style goniometers,
    new crystals and holders and additional instrumentation built and
    installed in the Tevatron.

5.  Continue to assess crystal collimation performance by producing a
    new goniometer**,** crystals and instrumentation for the Tevatron to
    be installed by the 2008 shutdown.

Our goals are measurements of:

1.  Channeled beam\*

2.  Volume-reflected beam\*

3.  Beam loss and radiation levels downstream of the crystal setup

4.  Beam loss rate in the B0 (CDF beam-halo monitors) for 1- and 2-plane
    collimation

5.  Possible deformation of the crystal or crystal holder during a
    vacuum baking process.

6.  Attempt to study crystal damage: shock and integrated dose.

(\*) Add dedicated beam diagnostics

Quantitative measure of collimation efficiency improvement is reduction
of (3) -- primarily an LHC concern -- and (4). We are going to simulate
the deflected beam loss in the Tevatron and LHC (in collaboration with
IHEP and CERN colleagues). Consistency with the current secondary
collimator and absorber layout is of a concern here. This needs
simulations and optimizations.

Deliverables:

1.  Conclusive data and directly relevant input for decisions on a
    possible upgrade path for LHC collimation: improved collimation
    efficiency and reduced irradiation of downstream components in a
    quantitative agreement with corresponding calculations, and
    quantitative answers to the questions on damage limits and
    sensitivity analyses.

2\. Crystal technology, process (channeling or volume reflection),
hardware (goniometer etc.) & instrumentation most suitable for 2-plane
collimation of LHC beams, transferred to CERN.

## Phase I

Our plan for the remaining part of 2007 is

1.  Initiate studies of new possibilities for collimation exploiting
    volume reflection.

2.  Try to demonstrate channeling with the existing strip crystal and
    confirm the 2005-2006 result that crystal channeling and volume
    reflections can improve the Tevatron collimation system efficiency.

3.  Initiate design and manufacturing process to replace the existing
    goniometer.

4.  Initiate detailed simulations of collimation system performance with
    a single strip crystal in the realistic Tevatron lattice for both
    channeled and volume-reflected beams.

5.  Work out a plan on beam diagnostics improvement and installation of
    the new goniometer for the 2009 beam studies.

Our plan for calendar 2008 is

1.  Build improved beam diagnostics system and new Ferrara goniometer.

2.  Develop new strip and multistrip crystals.

3.  Complete end-of-store studies and proton-only store angular scans
    with the crystal chosen in 2007.

4.  Perform detailed simulations for a complete two-plane crystal-based
    Tevatron collimation system.

5.  Try to perform tests to provide information about the possible
    deformation of the crystal or crystal holder during a vacuum baking
    process (up to 200 degrees).

6.  Investigate a possibility for a crystal damage experiment where
    crystals and instrumentation for assessing dose rates could be
    placed in the Fermilab beams. Once enough beam is integrated on one
    crystal, it should be moved back to CERN for H8 beam line
    characterization.

## Phase II

The goal for 2009 is to demonstrate efficiency of a well-prepared bent
crystal collimation system for 2 planes with channeled and
volume-reflected 1-TeV beams at least for two crystal types (single and
multi-layer) in comparison with tungsten target results.

Our plan for 2009 is

1.  **Install New Hardware:**

-   Remove E01 collimator to replace with vertical crystal assembly

-   Crystal, goniometer, instrumentation tunnel installation

**2. 150-GeV Beam Tests (1.25 shifts):**

-   Test BLM response, inchworm and channel the beam

-   Debug all motion control and instrumentation

**3. 980-GeV End-of-Store Beam Studies (4.75 shifts):**

-   Find and characterize channeling (V-plane)

-   Collimate channeled beam (V, H)

-   Collimate volume-reflected beam (V, H)

-   Attempt full channeled collimation (V&H)

-   Attempt full volume-reflected collimation (V&H)

-   Repeat with another crystal type

# Outlook

August 2007's Accelerator Advisory Committee at Fermilab fully supported
this unique opportunity to perform dedicated end-of-store beam studies
in the Tevatron in order to (1) confirm the Accelerator Science of this
phenomenon, and (2) build a case for an LHC implementation. It called it
"an experiment with great potential which could definitively establish
the multi-turn physical model, building on the recent single-pass
success in the H8 beam line at the SPS; it could revolutionize
collimation systems in the LHC and other future accelerators".

It stated that LARP is an appropriate vehicle through which such a
"high-risk, high-gain" activity could be coordinated. FY08 & 09 planning
should become a high priority for LARP Accelerator Systems management.
The AAC recommended:

-   To enhance beam diagnostics, perhaps even including single-particle
    tracking capabilities.

-   Invite particle physicists to join the experiment, the approach
    proven to be very effective, e.g., in the SPS H-8 experiment.

-   Beam time planning for 2009 should depend on reasonable
    demonstrations of success in 2008.

## Rough Estimate of Cost and Timeline

CERN support: \"In view of the possible limitations for conventional
collimation like implemented for the LHC start-up, CERN is presently
investigating possible paths to enhancing the efficiency of the LHC
cleaning systems. The use of crystals has been proposed as one
possibility for improving collimation. However, a clear demonstration of
improved collimation efficiency in an existing storage ring is still
missing.

The CERN collimation team therefore fully supports the proposed
experimental investigation at the Tevatron. The support will include
advice on important experimental observables, participation to beam
tests and help for analysis of recorded data. It is our hope and
expectation that Tevatron beam tests on crystal collimation provide
conclusive data and directly relevant input for decisions on a possible
upgrade path for LHC collimation.\"

CERN: Experiments at H-8 beamline, manpower, beam characterization of
"TeV" crystals to guarantee success at Tevatron

INFN: manpower, crystal preparation, etching, mechanical and optical
characterization, goniometer (100 keuro)

IHEP: manpower, crystal preparation, etching, characterization;
simulations, new crystal technologies

PNPI, JINR: manpower, theory, simulations, beam diagnostics, DAQ, new
crystal technologies

KEK: manpower, beam diagnostics

Fermilab: manpower, crystal and other hardware implementation in the
Tevatron,

EOS beam time, beam diagnostics, DAQ, simulations, deformation/damage
tests

SLAC, BNL: manpower, beam diagnostics, deformation and damage tests

Ferrara is ready to take the responsibility and the charge of building
the goniometer and eventually incorporating the most appropriate
crystal.

A preliminary request has been made by Walter Scandale of funding this
experiment at the INFN CSN1 (the body in charge of funding experiments
in the INFN). The basic idea described was to install roman pots with 
scintillation fibers, silicon strips and whatever appropriate, upstream
of the secondary collimator at FNAL, a second goniometer for crystals at
the location of the primary collimator and additional  detectors in at
least another position downstream of the secondary, with very
encouraging answers and the request of better  defined plans.\
\
Initial points to be considered are the following: roman pots, detectors
and electronics;\
radiation hardness; space; occupancy; integrability of existing roman
pots to the FNAL vacuum pipe (from  TOTEM, from FPD, or from ZEUS);
constraints induced by the FNAL standards; cross-qualification with LHC
design and cryogenic standards; control system; counting room.

Beam studies: parasitic approaches in preparing the circulating beam;
beam instrumentation (list of possible improvements to the existing
ones); special software; sharing the tasks and the financial loads.

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