# MEMORANDUM 

**To:** Distribution

**From:** F. Dylla

**Subject:** FEL Upgrade Project Weekly Brief - November 14 - 18, 2005

**Date:** November 18, 2005

**Highlights:**

This was a good week for the FEL Upgrade. The hard and careful work by
the FEL staff and our JLab collaborators during this shut-down period is
beginning to pay-off. As of this writing the SRF commissioning team
headed by Mike Drury and Tom Powers is completing the re-commissioning
of the 3rd cryomodule after its vacuum cycle and window replacement. As
noted in the WBS 6 (RF) report below, the FEL 3 module is capable of
delivering at least 46 MV. The entire linac (the injector cryounit) and
the three linac cryomodules have now been re-commissioned. The linac
should be capable of producing 125MV of acceleration (on crest) and
123MV at our usual acceleration conditions (10\^o off crest). This
should give us some head room for our planned 10 kW operation with the
new wiggler which needs 115MV.

Other accomplishments include:

-check-out (by direct in-situ measurement) of all of our QX quadrupoles;
they are settable within a range of ± 2.5 parts per 1000.

-check-out of all the vacuum interlocks

-check-out of 90% of the SRF interlocks

-the dump ceramic was replaced, electronics re-installed and shielding
replaced

In addition, some operational time was put on the clock this week with
continued injector set-up and analysis of our first signals from our new
Beam Position Monitors (BPM)

We received notice of award for two JTO proposals having to do with high
power optics design.

See the report under WBS 11 (Optics) for details.

Next week is a short week due the Thanksgiving break. In the first part
of the week we will continue injector set-up, put additional run-time on
the rf systems and continue the check-out of diagnostic systems.

There will no weekly report next week. We wish all of our readers and
collaborators a healthy Thanksgiving dinner with friends and family.

**Management:**

Several members of the FEL team (Neil, Rode, and Jordan) attended this
week's DEPS symposium and reported on our developments with our photogun
and FEL optics.

The ONR project financial report for October was completed and forwarded
to the DOE and ONR program offices.

On Thursday we were visited by the CEO and Technical VP of the National
Electrical Manufacturers Association to discuss technology transfer
issues.

Gwyn Williams gave an invited talk at Teratech 2005 in Osaka Japan, and
represented the USA in a joint USA/Japan/EU THz Network meeting.

**WBS 3.0 (Beam Physics)**

Continued flogging the MADMAN program. Cooked up machine recovery
metaprocedure, which, with update of injector procedure and high current
recovery procedure describes a path back to 10 kW.

**WBS 4 (Injector):**

Injector and DC Photocathode gun are both operational. PARMELA modeling
of the injector continued this week.

**WBS 5 (SRF):**

[100 mA 750 MHz FEL Injector Cryounit Progress]{.underline}

-   The third harmonic cavity is assembled into a test stand and ready
    for VTA testing. The testing of the cavity is scheduled for next
    week after the completion of our current VTA shutdown for scheduled
    maintenance.

-   Cavity helium vessels are scheduled to be delivered to AES this week
    for QC/QA inspections. Shipment to JLab is expected the last week of
    November. A fundamental cavity will go back into the VTA next week
    in order to verify the warm-to-cold frequency shift. This
    information is needed to specify the warm tuning of the cavity prior
    to helium vessel welding.

-   A confidential disclosure agreement is being put into place between
    JLab and the fundamental power coupler vendor in order to facilitate
    the exchange of information needed to properly inspect and process
    the FPC's next month.

-   The hardware for the bench top warm tuning modification is due in
    next week and will be installed and test fit with a cavity for
    functionality. Engineering design continues on the remaining tooling
    modifications.

-   In light of the Renascence HOM issues, we should revisit the plans
    for the 100mA HOM feed through and the coax cable thermal anchoring
    design.

**WBS 6 (RF):**

Commissioning effort on zone FEL3 took place this week.  We determined
the maximum gradients and did a one hour run at this gradient.  By noon
Friday we were testing the last cavity.  The cryomodule looks like it
can produce about 46 MV of accelerating gradient on crest.  During the
test the field probe calibrations were determined based on the values
imbedded in the control system.  There seems to be a mismatch between
the forward power and the accelerating and the loaded-Q on cavities 4
and 6.  Assuming that the field probe calibration in the control system
is correct these two cavities could only produce about 4 MV/m each.  We
will be spending Friday afternoon and early evening recalibrating the
gradient on these two cavities.  Assuming the 8^th^ cavity has a
reasonable Qo value at high gradient it is expected that the zone will
produce less than 200 W of RF heat load at maximum gradient.  This
should be sufficiently low for operations.

We validated 90% of the cryomodule interlocks.  This includes the vacuum
interlocks and all of the arc detector interlocks.  We have tested about
half of the window temperature sensors.  The testing included functional
tests, which also validated the cabling and controls interface for each
channel.  Zones 2 and 4 were operated and the relative maximum gradients
were determined.  We are investigating some minor hardware changes that
will allow us to better optimize the control loops.  It looks like the
on crest machine energy is about 125 MV (Possibly greater depending on
the calibration issues relating to cavities FEL3-4 and 6).

Two potential cavity "interlock" problems were identified.  The first is
that failure of an auto test of the arc detector system does not inhibit
the operation of a cavity.  I have requested that the software group
implement a change such that failure of an arc detector test will trip
the cavity off and provide an indication on the operations screens.  The
second is not a fault but still not a desired condition.  Typically when
a cryomodule is turned on for the first time after a few days of being
off, one or more of the cavities is detuned sufficiently that the cavity
does not produce gradient.  On the cavities with better window vacuum or
no window vacuum space, such as our new style cryomodules, the control
loop tries to drive the cavity harder until the klystron is at it's
maximum power and there are no faults.  While this does not cause an
immediate problem and windows are tested at twice the power capabilities
of the installed klystrons, it is not a desirable operating point. 
Until a software control algorithm can be developed, operators have been
advised to watch for this condition and take appropriate action such at
the cavity does not remain in this state for more than a few minutes.

Problems fixed during the week.

Buncher klystron water flow problem.

Arc detector on FEL3-2 failed and replaced.

SRF commissioning software improved.

Problems needing attention.

Two software changes for LLRF to address off normal conditions.

LLRF in zone 3 cavity 8 needs attention.

**WBS 8 (Instrumentation):**

Hot Check-out and System Readiness for the restart of regular beam
operations has been our primary focus this week. Since we locked the
machine up early each day, please note that all of the vault activity
took place each day before 9:00. A special thanks to everyone who came
in extra-early to make this week as productive as it has been.

\*\* RF Instrumentation \-\-- To support the commissioning of the Zone 3
cryomodule the RF interlocks for the cold cathode gauges were all
installed. The cold cathode gauges provide the Wave Guide Vacuum
interlocks for the zone, since there are no wave guide vacuum interlocks
on the zone. The analog readbacks for the gauges have been patched into
EPICS. The logarithmic scaled output has been converted back to a linear
scale so the ADC can give the accurate vacuum reading.

\*\* Beam Current Diagnostics \-\-- The 1G03 Dump Electronics have been
installed at the 1G03 dump. The new electronics have been calibrated
through EPICS and verified that the scale of 1mA = 1V is consistent
throughout the input range. The shielding blocks for the dump have been
reinstalled and the steel shielding will go in as soon as time in the
vault is available. The new User Beam Current Monitor electronics have
been installed and the necessary cables installed. Once the beam line
hardware is installed the connections will be made and the readout
should be available in EPICS with the other dump and BCM signals.

\*\* Vacuum System \"Hot Check-out\" \-\-- Every ion pump has been
tested as well as well as all of the Convectron gauges. We verified that
the vacuum system channel designation is truly the hardware being
controlled. The channel connections are correct to the Vacuum System
Crates in FL05. A few problems have been discovered in the vacuum crate.
VIP1V00F readback is just noise, VIP5F00 interlocks (in the vacuum
crate) are not operating and have failed-safe. Once these issues are
resolved, the vacuum system will be ready for operations.

\*\* \"NEW\" BPM Electronics \-\-- One of the new BPM Electronics was
installed in the 0F region in order to take some data with the FEL
injector beam. This set of electronics has the updated code that uses
the sPline interpolation. Data will be taken as soon as injector
operations begin today to get a feel for exactly how our system will
behave. Firmware files for the next revision of the board are being
developed. The board, brackets, and wiring have all been installed for
the sextuple reversing switch. The enclosure wiring will be documented
so all switches will be consistent. \-\-- Also, The subrecord for sPline
interpolation is programmed. The subrecord would call the function to
initialize the sPline interpolation by using the data from calibration,
and then it would call the Splint function to do the real-time
calculation to obtain the beam X, Y position. A new application code and
database were made and installed in a ColdFire BPM. The new BPM is
running on FEL. We checked the result, and it matched with the
calibration curve.

\*\* Magnet Power Progress \-\-- Another schematic has been submitted
for a check print for the revisions on the GC power supply boards. The
GC power supply has been inserted into EPICS controls and is functioning
properly. A new print should be approved by next week, and work on
fabrication of new boards should commence shortly. Also, we are
populating 10 of the 6kW Reversing Switch circuit boards. We have
assembled a new Charge/Dump Current Monitor Buffer Driver Box and we are
setting up a test fixture for the Video/Crosspoint circuit boards for
trouble shooting.

\*\* Wiggler Controls \-\-- The ethernet communication to the wiggler
has been problematic and we\'ve spent a lot of time troubleshooting
that. The serial communication seems to be fine. The issue was resolved
just today.

\*\* Emittance Monitoring \-\-- Video interlacing is distorting the
horizontal multislit measurements. Interpolating the image works well
for normal beam, but is failing for the small beamlets. We are working
through this during beam operations.

\*\* Miscellaneous Activities \-\-- The Happek (Interferometer) was
aligned with help from the optics team (Thanks Joe!). The Fresnel lens
and insertion track were secured in place and aligned. We still need to
connect the air to the Happek stage and connect the control line to the
control system upstairs. \-\-- The viewers in the vault have all been
basically hooked up and just need a little aligning here and there.
Currently, each viewer is at least hooked in and 95% aligned. \-\--
Cable was also run for the wiggler control box from the control room in
order to provide basic control over the box so programming and
controlling can begin in EPICS. \-\-- The lab 2 cables for the LPSS
system have also been moved/run. The shutter lockout box cables have
been run from the LPSS box to the other side of the lab and excess cable
is in place for placement of the lockout box. The other cables for the
CAN and Mirror cassette have also been rerun to the new location of the
can. \-\-- Support for the completion of the optical beamline in the
back of the labs was begun also. Cables were run for the Ion pumps and
Convectron Gauges in labs 5 and 3a. Beamline valve cables were also run
for the valves in labs 5 and 3. The cables for the Ion Pumps and
Convectron Gauges have been appropriately dressed in with black flex.

Lastly, a \"System Readiness\" page at:
[http://laser.jlab.org](http://laser.jlab.org/) has been set-up to
provide a definitive list of the various systems of the FEL. It will
take a few weeks to get the list filled out completely and to have the
information listed correctly. But this page will be referred to
regularly from now on.

\- rich (on behalf of the I&C group)

View \"fel_ctrls\" archive at:

<http://www.jlab.org/ccc/mail_archives/ACCELERATOR/fel_ctrls/CURRENT/>

# 

# WBS 9 (Beam Transport):

# *Sextupole (SF)*

• Over the next week the magnet test stand will be off the project,
devoted to a 12 GeV dipole magnet test.

• We mechanically measured the #11, the magnet that was giving us
sideways fields. Results show that it doesn't have any gross mechanical
errors. This convinces us that we may be looking for very subtle causes
of our out-of-specification readings. There may be some probe in the
right position problems.

• Basically the quadrupole term went away at the high and low currents
and remained at intermediate currents after we tightened the bolts. This
may indicate non uniform residual fields are the cause. In our proposed
tests the week after next, we will try splitting the operating range
into two or three zones with lower maximum hysteresis cycle currents for
the lower ranges. This technique worked on the GX dipoles. We also plan
a series of magnet measurements to assess the sensitivity of various
pole movements and field clamp movements to field quality.

**Replacement Chicane Dipoles (GW)**

• The remaining two units in at Magnet Test, awaiting the testing of
Sextupoles before the GWs get measured.

**QX Quadrupole Measurement**

• The folks at Argonne APS had a similar problem measuring their
quadrupoles, They get relative strengths of parts in 10,000 on a
rotating coil stand but can only get absolute strength at the parts in
1000 level. We will not be using their facilities.

• With this finding (that according to Tommy Hiatt is echoed by the
measurement folks at other labs) David Douglas writes: "Methinks a
rethink of philosophy is in order. I suspect that we should map a
standard and a few references as well as possible, and then characterize
the whole lot relative to the standard and scale on the machine."

# *UV Line*

• Meanwhile, quads are not tested and girder assembly remains on hold
until UV funding is secured

• The NEG Pump cartridge holder design for the second corner UV chamber
is also on hold.

# *UV Wiggler Progress*

•     No progress on the new Wiggler vacuum chamber.

# *IR Machine Quadrupole Operations*

•     Lots of folks did a lot during this down period to address the
causes of David Douglas' discontent with quadrupoles and their power
supplies. Several of the 5F quadrupoles had low loss cables installed so
they could reliably not trip during hysteresis loops. All trim cards
were modified so they would not trip upon turn-on. The entire trim rack
system was given a tune-up; connections were tightened and faulty
elements discovered and replaced.

• Of even more importance, contact with the folks who repair the system
were solidified. With the tune-up accomplished, the failures of the trim
racks and cards will be reduced so that it will not overwhelm the
system. Rather, we are determined to use the formal paperwork tracking
systems that are already in place so we will not let failures go
un-resolved.

• We made a big increase in our ability to diagnose problems with the QX
quadrupoles as detected by beam operations. After the tune-up, we used
the field measuring probe fixture, so ably developed by the shop. We
found that it gets reproducible readings, to the gauss level, for 3 or 4
pole gaps in the QX quadrupoles. It enabled us to detect one trim card
that was 5% out of calibration. After recording field values for the QX
Set at half maximum field, we have a baseline to track drift or
calibration problems in trim cards and changes in the quadrupoles. In
addition, using the fixture and probe enables us to qualify or reject
exchanged trim cards when the installed cards fail.

**WBS 11 (Optics):**

***FEL mirrors***

The HR and OC assembly\'s leadscrews were conditioned to allow for a
faster mirror changeout.  Mirror alignment will commence today.  We are
procuring witness samples of our mirror substrates to send to several
coating vendors.  The output of the master oscillator for the advanced
drive laser was realigned through the amplifier chain.  We are making
48W of IR with the MO configured for low phase noise, compared to 50W
when in the high phase noise regime.  We can make up the necessary
delta, if needed, by slightly raising the pump diode power. We need the
advanced drive laser as a surrogate for calorimetry and laser damage
testing.

***Other Activities***

A vexing leak in the optical transport system (OTS) section in User Lab
1 (UL1) was found and fixed.  We should be able to pump that section to
the point that the vacuum interlocks will permit the valve to be
opened.   Work continues on the THz pump probe system.  The plan is to
measure the phase noise of the electronics this weekend. (the only time
we can have the new phase noise measuring system). The ultrafast laser
system, now situated in the THz hutch, is coming back to life.  The pump
laser was successfully run.  The oscillator is out of alignment, so
some work there is required, as well as a safety shutter added.  The
extinction ratio of the EO cells for the drive laser were measured
individually, and each found to be \~ 100:1.  This should be sufficient
for operations.  The first EO cell had a damage spot that scattered
light, and was replaced with the spare.  A new one needs to be
purchased.  A shorter work table was moved into the drive laser Clean
Room to complete an action item submitted by EH&S.   The vacuum vessel
for the DIRUP-funded (to the College of William and Mary) \"pulse
stacker\", an external cavity for the FEL, was assembled, aligned, and
is under roughing vacuum.  We welcome Michael Klopf, a postdoc working
on the THz project, to our trailer.  We were pleased to learn that we
are being awarded contracts by the JTO for two projects entitled \"Short
Rayleigh Range FEL Operation\" and \"Advanced Figure Control\".  We will
also be subcontracted to work with Dr. H. Freund (SAIC) for his contract
\" Modeling and Simulation of the Effect of Mirror Distortion
on High-Power FEL Oscillators\".Measurements started on the flow-induced
vibration of our mirror geometry.  We need this to determine the limits
to the flow of \~50K helium, a Navy priority.

***Terahertz:***

This week we welcome Michael Klopf to the FEL group, with special
responsibility for the THz laboratory.

We received the critical Picarin lens for our next imaging experiments.
The specifications for an ultrafast hot-electron bolometric detector
were finalized.