# MEMORANDUM 

**To:** Distribution

**From:** F. Dylla

**Subject:** FEL Upgrade Project Weekly Brief - November 7 - 11, 2005

**Date:** November 11, 2005

**Highlights:**

This week we continued our progression from system check-out to start-up
of operations.

Highlights for the week included:

-successful final leak check on the FEL03 cryomodule rf windows,
followed by cool-down to 2k on Wednesday; concurrently the rf waveguides
were hooked up and the process of check-out and re-certification of the
rf interlocks continued through today

-the alignment and vacuum activities in the wiggler region of the
machine were completed this week; the entire machine is now under vacuum

-injector activities continued this week during late first shift
activities; high quality signals were obtained on the "multi-slit"
emittance diagnostic

-the Optical Transport System from User Lab 2 through 6 is now under
vacuum

Next week we will shift the remaining punch-list activities to very
early in the day 0500-0900 and devote the majority of the working day to
re-commissioning of FEL03 and then move on to re-establishing linac
operations.

**Management:**

We worked on a draft report of FY05 accomplishments for the Navy funded
FEL program. The format for this report and the subsequent
cost-performance reports for FY06 were reviewed with ONR program
management.

The project financial reports for the month of October were completed
and will be sent to the respective program offices next week.

All FEL program cost account managers met today to continue our planning
for the optimal use of our resources in FY06 to meet the established
list of high level goals (which start with 10 kW operations at 1.6
microns).

Gwyn Williams gave an invited talk at a THz Systems Workshop in San
Diego.

**Operations:**

While we are waiting for zone 3 to be commissioned we are working on
commissioning the injector. We ran tune-up beam to the injector
dump this week and checked out all the magnets and diagnostics. We also
tried increasing the injector energy to take advantage of the increased
gradients available after helium processing. With field emission at
levels comparable to what we had before at 7.3 MeV/c we now can run at
8.7 MeV/c. The spot size after the cryounit is much smaller than at the
lower energy. With this beam we checked out the magnets in the injector.
The new vertical corrector embedded in the first quadrupole after the
cryounit now works and allows us to correct the vertical trajectory
after the unit. This corrector replaces two correctors spread over a
large section of beamline that had low magnetic field quality.

All the diagnostics present before the down still work fine. The new
emittance measurement multi-slit is now working. We took data with it
(see figure below) to measure its linearity and alignment. This should
be a very useful diagnostic for beam setup. We are now commissioning the
new BPMs in the injector. So far the injector is behaving quite well,
with few problems to date.

![](media/image1.jpeg){width="5.059027777777778in"
height="3.604861111111111in"}

**WBS 4 (Injector):**

Injector setup continued this week by threading down the beam from the
gun to the injector dump at 8.7 MeV/c. Preliminary PARMELA simulations
at this energy show a horizontal longitudinal distribution with \~ 10keV
energy spread and 2.5 ps rms bunch length. Both vertical and horizontal
multislits were operated successfully as well as the data collection
software developed by Pavel Evtushenko and integrated by Wes Moore.

**WBS 6 (RF):**

During the past week we continued to prepare cryomodule FEL 3 for
commissioning. SRF staff reconnected the waveguide between the klystrons
and the cavities. EESRF staff found a leak in one of the waveguide
joints and repaired it. PSS staff completed the PSS certification for
the zone; this included bringing the zone up to the high voltage mode.
The window IR and arc detector sensors were installed, the channel
mapping and functionality of each was verified. We did a complete
checkout of the interlocks for the zone except the new coupler vacuum
interlocks, which are in the process of being verified. 

We brought cryomodules 2 and 4 on line and characterized the klystron
capabilities, including body currents for zone 4. The LLRF output
attenuators were set on zone 4 to insure that the klystrons are not
operated beyond the desired maximums. We found that cavity FEL2-8 has a
thermal quench at 7.25 MV/m and a klystron body current limit at 6.5 kW.
We made adjustments to the LLRF output attenuator and the maximum
allowed gradient settings in order to insure that these fault limits
would not be exceeded. 

**WBS 8 (Instrumentation):**

We have had an excellent week beginning to commission the various new
and upgraded diagnostic in the injector. Most notable was the multislit
emittance monitor. We have had a few versions over the year that were
marginally succesfull. The improvements were three fold; 1. separated
the horizontal and vertical slits to allow for accurate alignment, 2.
EDM wire cut new slits (they look like a mans pocket comb)out of Nb (we
had a few scrap pieces\...), and 3. the DESY style phosphor coated
viewer paddle. (see highlights for image)\
    Progress continues on commissioning of the BPM electronics. A series
of characterization measurements were made is to better understand the
how each channel will function.  The first measurements that were made
were setting the initial calibration points via the zero adjust and then
the slope adjustment.  Once these points were set a series of data was
taken as the input power was varied from -60 dBm to 10 dBm with steps of
1 dBm.  These points were plotted for each channel and then error
measurements were made as a function of input power.  The results of
these measurements show that the current technique for calibrating the
position gives as much as a 2mm error at certain input powers.  So in
order to handle this error a spline interpolation is being made in the
on board processor based on the channel to channel variations. 
According to the measurements this should improve the error down to a
maximum of 200 microns.  This software change is being made at this time
with the hope to be able to test with the FEL injector.  The other
measurements that were made so we can try and get the bandwidth of the
system in the most operable point of FEL operations.  The zero crossing
point was swept across a range of 10 dBm and the slope was altered to
get the maximum output of the system for 10 mA operations.  These
bench measurements are useful in identifying the problems with these
electronics and help provide the data needed to correct them. A scanning
wire calibration stand is being designed to determine the actual
resolution (both short and long term) of the electronics. A spline
interpolation is also being programmed for each channel of the BPM. A
set of points of rf power (db), and a set of points of  volts from each
channel are obtained from calibration and used as inputs for spline
interpolation. The subroutines for all four channels are coded. I am
going to make the subrecords and new database for the x, y position
calculation.

Calibration of the new 3F viewers began this week. The cameras were
positioned to the standard height. The mirror positions were adjusted to
fine tune the size of the foil on the screen. A WesCam calibration was
done for the completed viewers. ITV0F04 was replaced this morning after
some WesCam triggering issue. The fix will be tested during today\'s
shift.

The EPICS cubic spline fit for the wiggler K to gap calculations was
tested successfully. The safe guards for the wiggler gap size will be
implemented and fully tested before the software goes into operation.

    All of the parts except for one have arrived for the sextapole
reversing switch.  The boards have arrived; one has been populated
and tested successfully.  The brackets for the enclosure have all
arrived as well and the enclosure has been fitted up with the
electronics, brackets, and wiring.  The rest of the boards are being
assembled at this time so they will be ready for installation once the
last part arrives.

System checkout / Ops support continued this week with the semi annual
PSS certification. Functional testing of our major systems Personal
Safety System interlocks was completed. With the exception of 2 box
supplies all other interlocks passed. These 2 box supplies (2G Dump
Spectrometer, 2nd Arc String) have been repaired and should be tested by
end of business this week.

**WBS 9 (Beam Transport):**

# *Sextupole (SF)*

• At week's end our magnetic measurements showed horizontal field where
there should be none when scanning the horizontal mid plane. We found
that some of the above reading may be due to the test stand itself. We
found that perturbing the field clamp positions results in changes to
the horizontal field. Identical magnetic readings at the pole tips
indicate that the turns in the coils are all the same. Mechanical
measurements of a second magnet showed no pole positions or field clamps
significantly out of position. In all, we have more questions than
answers.

• Over the next two weeks we will mechanically measure as many magnets
as possible to allow us to correlate field quality with physical
dimensions. The magnet test stand will be off the project, devoted to a
12 GeV dipole magnet test. In the interim we will plan a series of
magnet measurements to assess the sensitivity of various pole movements
and field clamp movements to field quality, with the goal of finding and
eliminating the quadrupole and dipole components we see in these
sextupoles.

**Replacement Chicane Dipoles (GW)**

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

# *UV Line*

• Meanwhile, quads are not tested and girder assembly remains on hold.

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

# *UV Wiggler Progress*

•     No progress on the new wiggler vacuum chamber until new funds are
identified

**WBS 10 (Wiggler):**

The rest of the vacuum chamber around the wiggler was installed this
week. We are now hooking up the rest of the diagnostics around the
wiggler. Final alignment was completed this week as well. We have a few
punch list items to complete and then the IR wiggler will be ready for
beam.

The UV wiggler is in the magnet test facility at STI Optronics. First
measurement results should be available early next week.

**WBS 11 (Optics):**

***FEL mirrors***

The HR and OC assembly\'s ancillary diagnostics were checked out.  We
are ready for ops.  We have initiated discussions on coating work with a
few other vendors that use different deposition techniques than the one
we currently use (ion beam sputtering).  In order to move forward on our
absorption measurements, we\'ve moved the calorimeter to User Lab 6, in
order to use the advanced drive laser.

***Other Activities***

Early this week we started leak checking the newly-built optical
transport system (OTS) that exists between User Lab 1 (UL1) and UL6. 
There were numerous small leaks that were systematically found and
fixed, this consumed about 3 days for a portion of the group.  Work
continues on the THz pump probe synchronization electronics.  We need to
add some low phase noise signal processing components to properly shape
the clock signal.  A requisition for a new pump laser diode for the
maser oscillator was placed.  The original laser diode failed
prematurely, but well out of warranty.  The vendor will sell us a
replacement at a greatly reduced cost.  This way we\'ll recover the
ability to operate the laser system ay 748.5 MHz.  We also purchased
some beam condensing optics for the master oscillator that will decrease
the beam size in order to use a transverse EO cell for pulse selection. 
The extended range NIR camera was installed so we could observe the
fundamental laser mode on the HR mirror at wavelengths shorter than 1.8
microns.  Several of us are completing input to the FY05 annual report.

We received the thermal isolators, for both the cooling loop and OC
mirror, as well as the metal bracketry for the UV optical cavities.  The
utility vacuum line is complete at a local machine shop.  It awaits leak
check.

***Terahertz:***

The spectroscopy chamber has been ordered.  Representatives from
Thermo-Nicolet visited to advise on the conversion of the Nexus
Michelson purged interferometer into a vacuum version, and components
were ordered.  Work continued on specifications of an ultrafast THz
detector.