1. Heinz-Dieter Nuhn – LCLS Undulator Group Leader May 14, 2009
Undulator Plans
Heinz-Dieter Nuhn – LCLS Undulator Group Leader
May 14, 2009

2. 25 Undulators Installed

3. Answers to Committee Questions
What in project scope activities remain for LCLS undulators? ANSWER:
There are 5 undulators more to be tuned, a total of 8 undulators to be installed.
There are also ANL BLMs in scope which need to be made.
What improvements can you anticipate in the area of undulators and undulator diagnostics for LCLS looking ahead to operations? ANSWER:
Upgrade of signal processing for existing BLMs to add integration capability.
K-vs-temperature calibration for undulator segments to improve the estimate of undulator K values at deviating temperatures.
Procurement of precision temperature sensors for undulator segments.
Procurement of additional ANL-Style BLMs (under consideration) some additional are now in scope, a full complement would need an addition to scope.

4. Answers to Committee Questions
Can you present a summary of ‘Lessons Learned’ from the undulator construction activities supporting LCLS?
ANSWER:
Tuned Undulators were initially stored in an uncontrolled temperature storage area (building 750 pit, ). We ended up re-tuning all undulators. Since we had no data and mechanical calculations would have been too complicated and expensive, we should have tested the temperature limit of undulators.
Interference fit of undulator shims and vacuum chamber occurred this was due to many design iterations of vacuum chamber. This should have been discovered at fully integrated model.
Heavier bolts should have been used to hold the pole assemblies to the titanium strong back.
Undulator feet design should have been finalized during final design review and not during measurement and implementation stage.
Longitudinal thermal expansion was not considered. Temperature excursions caused big problems for us.
Canted poles are a great idea. Without them, we would not have been able to set K to %, i.e., we would not have been able to set the gap to 0.9 µm with parallel poles.
Spending money on a good measurements lab is essential. We have had to overcome many unnecessary obstacles such as air conditioner failures, air compressor failures, space constraints, bad cranes, etc. These take up a lot of time and energy.

5. Girder Position / Temperature Stability
Temperature fluctuations and ground motion cause changes in
Undulator strength, which depends on
Temperature
Beam trajectory
Electron beam trajectory (phase errors) due to
Quadrupole position instability
Observed stability of girder positions and temperatures is better than expected.

6. Temperature at All Girders
Upstream U23
Center U23
Downstream U23
On Girder
Mounted to Undulator

7. Temperature Recording Girder 16
SHUT DOWN (UND INSTALLATION)
REPAIR OPPORTUNITY DAY (ROD)
HVAC SETPOINT ADJUSTMENT
50 mK

8. Girder 15 Movement (18 h) During ROD (11 h)
Mechanical Hysteresis
>1 µm

9. Girder 13 Stability During 19h Operation
200 nm

10. Girder Stability During 2008 Winter Break
RMS Position Change < 1 µm
Courtesy of Franz Peters

11. K Adjusted for Temperature Deviations

12. Use of (T-)Corrected K Values
TEMPERATURE CORRECTED K
K ADJUSTMENT RANGE
TAPER REQUIREMENT

13. Radiation Control and Monitoring
Undulator radiation damage is greatly reduced through Machine Protection System (MPS) hardware interlocks that inhibit beam to the undulator hall when
PEP/ANL type BLM signals are above threshold
Beam loss fiber signals are above threshold
Horizontal and/or vertical trajectory is outside ±1mm
Comparator toroids indicate beam loss.
Any of the upstream profile monitors is inserted
More than 1 BFW is inserted or a BFW is moving
A regular TLD monitoring program is in place (s. below)
A regular undulator replacement program will start soon (s. below)

14. TLD Readings at First Undulator
LOCATION
WEEK 1 PHOTON [rem]
WEEK 2 PHOTON [rem]
WEEK PHOTON [rem]
U25:ANL-BLM
0.081
0.106
0.051
U25: PEP-BLM
0.042
0.048
0.030
U25: Back +X
0.065
0.008
0.033
U25: Back +Y
0.012
0.071
0.064
U25: Back -X
0.039
0.026
0.029
U25: Back+Y
0.013
0.014
U25: Front +X
0.112
0.093
0.072
U25: Front +Y
0.217
0.105
0.110
U25: Front -X
0.046
0.055
0.025
U25: Front -Y
0.141
0.123

15. Dose During Initial X-Ray Operation
e-folding length 8.7 m
Increased TLD Readings are expected to be predominantly low energy synchrotron radiation, not to cause significant magnet damage

16. TLD Replacement Program
Thermo Luminescent Dosimeters (TLDs) are mounted inside the Undulator Hall and are regularly replaced and evaluated
Baseline 10/3/2008 – 12/9/2008 (10 TLDs)
Startup 12/12/2008 – 12/17/2008 (12 TLDs)
1st Undulator 1/28/2009 – 2/4/2009 (15 TLDs)
1st Undulator 2/4/2009 – 2/11/2009 (14 TLDs)
1st Undulator 2/11/2009 – 2/18/2009 (18 TLDs)
1st Undulator 2/18/2009 – 3/2/2009 (48 TLDs)
FEL Operation 3/24/2009 – 4/22/2009 (68 TLDs)
FEL Operation 4/22/2009 – 5/6/2009 (125 TLDs)
FEL Operation 5/6/2009 – … (128 TLDs)
FEL Operation …
Latest TLD placements include detection of neutrons and high energy gamma through use of moderators and Ti and Pb absorbers.
TLD volume is expected to taper down after initial observation period.

17. Undulator Replacement Program
Undulators will be periodically removed from the Undulator Hall to be re-measured at the MMF to check for radiation damage.
A “test”-undulator was re-measured after several weeks of beam operation. No damage was found.
First undulator that participated in FEL run is scheduled for re-measuring in June.
Depending on MMF availability, up to 2 undulators per month will be removed from the Undulator Hall for checking.
After the undulators have been found undamaged they will be reinstalled onto the original girder.

18. Summary
Undulator tuning and installation close to completion
Temperature and girder stability well within tolerance
Beam loss control and radiation monitoring is in place
High radiation levels at initial FEL operation are expected to be predominantly low energy photons that should not generate demagnetization
Electronics components may need additional shielding
Undulator replacement program will start soon

19. End of Presentation