1. Preliminary Review of LERF as Cryomodule Testing Facility for LCLS-II
03-04 August 2017 at Jefferson Lab.
M. Ross, SLAC
03-AUG-2017

2. Introduction:
Cryomodule testing for LCLS-II SRF production is on the project critical path.
Recent discussion with Jefferson Lab indicates a path to develop a tool that promises substantial schedule advancement.
The LCLS-II/JLab Cryogenic Systems group has prepared a proposal to adapt the existing Jefferson Lab Low Energy Recirculation Facility (LERF) for LCLS-II cryomodule testing.
includes a suggested plan for testing 6 to 8 cryomodules during the period mid-FY18 through mid-FY19.
LERF review, 03-AUG-2017

3. Any CM-repair/retest cycle will delay project end-date.
LCLS-II CM testing:
Cryomodule testing for LCLS-II SRF production is on the project critical path.
Each CM to be tested in-turn using existing test-stands, one at Jlab and one at Fermilab.
This ‘end-to-end’ scheme determines the project duration
In contrast CM assembly is not tightly infrastructure-limited; both production lines have some redundant infrastructure
However - Supply-chain, esp. qualified-cavities is an outstanding risk that may push project duration; i.e. beyond CM-test forecast.
Any CM-repair/retest cycle will delay project end-date.
CM test-facility downtime also is unrecoverable
LERF review, 03-AUG-2017

4. LERF review, 03-AUG-2017

5. LERF review, 03-AUG-2017

6. Typical CM test cycle
Prep  done outside test-enclosure; not included in cycle duration
Install
Cool-down
Soak
Check-out
Max Gradient determination
Full-unit operation
Q0-estimation
Warm-up
Remove
4 weeks; cold testing itself less than 50% of that
Recent testing has included LLRF system-qual and microphonics studies
LERF review, 03-AUG-2017

7. 7 test cycles are completed (or are now underway) since Oct 2016.
CM rework – an update:
7 test cycles are completed (or are now underway) since Oct 2016.
Six CM tested
37 to go, until early / mid CY2019.
4 CM have (or may require) retest (re-work, cross-test, severe repair)
Both test-facilities have been subject to cryo retro-fit downtime
Testing-duration has been extended (3 cycles) for technical studies: Microphonics, heat-stationing, fast cool-down
Delay roughly 10 weeks wrt initial plan (~ 2 ½ test cycles)
LERF review, 03-AUG-2017

8. Proposal (to be Reviewed):
The LCLS-II Cryogenic Systems group has prepared a proposal to adapt the existing Jefferson Lab Low Energy Recirculation Facility (LERF) for LCLS-II cryomodule testing.
includes a suggested plan for testing 6 to 8 cryomodules during the period mid-FY18 through mid-FY19.
Initial estimates show this to be practical at a fully burdened cost of about 4M$.
 The technical performance capability of LERF has been well established and should be well suited for this purpose.
LERF review, 03-AUG-2017

9. CM Testing – Test Facility / Linac - Differences
Neither (existing) TF can hold more than one CM
LERF allows two (possibly three) LCLS-II CM
SLAC linac has 12 CM-long monolithic segments; Interconnect can be tested at LERF
Better test of linac cool-down process
Neither TF provides nominal-temperature input 3-Bar He
LERF uses CHL JT HX (similar to SLAC design)
(Test Facility input He ~5K)
LERF operational pressure  2.07 K, above nominal LCLS-II 2.0 K
LERF review, 03-AUG-2017

10. The most severe risk is interference with ongoing CEBAF operations.
Risks:
The most severe risk is interference with ongoing CEBAF operations.
CEBAF-cryo have procedures for connecting a warm CM into the operating sub-atmospheric system
Operations – schedule planning strategy important
LERF uses the main CEBAF south linac CHL refrigerator.
Contamination and/or pressure transients in the 2.07K sub-atmospheric helium circuit are the primary concerns.
LERF review, 03-AUG-2017

11. Please:
Review the feasibility of LERF-SRF CM test facility proposal to advise the LCLS-II project:
Is the overall plan reasonable,
Is the scope of work practical,
Is the schedule consistent with the available resources,
Is the expected LERF cryogenic systems performance consistent with that needed for testing LCLS-II cryomodules,
Is the plan for managing the work and the testing consistent with project requirements, and
are the risks, especially the risk of interference to CEBAF operation, properly understood and mitigated?
LERF review, 03-AUG-2017

12. Feasibility Review Charge Questions:
LERF review, 03-AUG-2017