1. Conceptual design of the Cornell ERL Linac Cryomodule Eric Chojnacki Cornell University Laboratory for Elementary-Particle Physics Cornell ERL Director’s Review, August 2-3, 2007

2. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 2 Outline  ERL cryomodule philosophy  HTC and Injector experience  ERL linac cryomodule layout  Linac cryogenic Loads  Items requiring development  Industrial role  Linac test modules

3. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 3 ERL Linac Cryomodule Philosophy Use the same cryomodule concept in the Injector and the main linac. Rely on well established and tested performance of the TTF III technology to reduce risk and minimize development time. Simplify and reduce cost.

4. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 4 ERL Cryomodule Innovations Precision fixed surfaces between the beamline components and the HGRP, easy “self” alignment HGRP alignment possible with the Vacuum Vessel under vacuum and cold Rail system for cold mass insertion into Vacuum Vessel Tuner stepper easily replaceable while string is in cryomodule WPM with simple electronics 80K and 5K He HEX in Cryo can In-situ bake for cold and warm couplers, no further atmosphere exposure, no pre-conditioning

5. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 5 ERL Injector Components He Gas Return Pipes (HGRP’s)Support post assy Post alignment assy Shields Vacuum vesselHOM loadsSRF cavity Warm-up/Cool-down tube HOM load Mumetal Shields Cryoperm Wire position monitor 80K return 80K supply 5K supply He Gas Return Pipe Vacuum vessel Support post alignment Rails Support post 80K return 80K supply 5K return 2K – 2 phase line HOM support 1.8K cavity 80K HOM load and shield 5K beamline intercepts 300K exterior support

6. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 6 ERL HTC Lessons 1.Only use tight specs on necessary dimensions. 2.Only use 316L where necessary, 304L as default. 3.Place mu-metal shield flush to Vac Vessel @ 300K to avoid 85% de-rating @ 80K. 4.Use formed bellows instead of expensive welded bellows on beampipe-VV adapters, and simplify the adapters. 5.Use formed bellows instead of expensive welded bellows on HGRP adjustment atop VV. 6.Use extruded Nb RF Input ports using a “puller” rather than an expensive solid Nb block. 7.Composite Post Supports machined after assembly for precision height 8.Vacuum Vessel: 1.Make the VV tube length an integral number of 8’ sheets (less 2” of trim) if close to an integral length. 2.Spec to tight tolerance the Coupler Port flange final machining. 3.Eliminate the step in Vac Vessel flanges, use a simple flat face mate to another simple flat face with an o-ring groove. 4.Use simple flat “ears” for lift points instead of “Eye Bolt Boss”. 5.Use easier weld prep on VV Flanges. 6.Change the rail system weldment technique for easier alignment. 9.The “adjusters” on the composite post tophats need more adjustment throw, the brass toggle-feet presently have little wiggle room. 10.Mod 2K Return bellows for braided to prevent elongation or pressurized squirm. 11.The Clean Room String Assy fixture should have a 3-legged option for string raising when attaching string to HGRPs, as opposed to present 4-legged. 12.Can the tuner motor be placed further away, outside Mag Shield III? Re-think the blade tuner motor linkage. 13.Can the tuner piezos be located “inboard” of the He vessel flange for straight forward forcing rather than via bolts through the flange, to a block, and so on… 14.Re-think tuner piezo pockets with ball. They are difficult to insert and center. 15.Quantify cavity frequency/tuning error tolerance due to handling. Design the tuner frequency center point and range well outside of these error bars so that all cavities are comfortably/easily set up with the tuner in compression and piezos not falling out. 16.WPM: 1.WPM end ¼ plates made of Al instead of SST. 2.No bellows on WPM tube at end plates, just on WPM blocks. 3.WPM blocks made of aluminum for less radiation activation. 4.Eliminate intermediate Ti spacer block on WPM. Cu block screw direct to Ti arm with 2 precise surface specs on Ti arm (to He plate and to block). 5.WPM fiberglass wire clamps have V-grooves cut part way to guide the wire. 17.Consider tape for attachment of Mag Shields. 18.Simplify He vessel conflat port of Ti/Nb/SST, eliminate unreliable explosion bonded interface. 19.Any benefit to rotating the mag shield seams away from the stepping motor? 20.No need to face the entire end plates, give a generous flatness spec away from seal surfaces, but don’t allow excessive plasma-cut potato-chip. 21.Re-do 2K wiring and He level sticks, only 2 sticks. 22.Allow more orbital welder and fixture space for He plumbing ¼” tube welds, at least 2” of straight to all ends. 23.Eliminate many temperature sensors. 24.Find a less costly gate valve solution. Continuous Improvement: Linac cryomodule simplification and cost reduction

7. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 7 ERL Linac Cryomodule Layout Alignment tolerance of quad vs. cavity’s 1mm? Optimal number of support posts per HGRP? Optimal location of support post to couplers for acceptable CTE stress?

8. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 8 ERL Linac Cryomodule Layout Modeled Beam Optics Cryomodule 10 cavities 2 Quads and kickers per module Module is likely too long Next Beam Optics Cryomodule 6 cavities 1 Quad and kicker per module Could be extended to 8 cavities (12.6m) if beam optics allow 1 quad and kicker per module

9. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 9 ERL Linac Cryomodule Layout Cavities per cryomodule6 Cryomodules per linac16 # linacs4 # cavities384 # cryomodules64 Cryomodule length [m]9.82 Linac length [m]638.6 (2 x 319.3) Total active length [m]306.4 Module Filling factor0.49 Final energy [GeV]5.0 Gradient [MV/m]16.3 Linac A1 = 16 Modules Linac B1 = 16 Modules Linac A2 = 16 Modules Linac B2 = 16 Modules = 0.25m Cold-warm transition 317.3 m 4 m Open question of having: a) continuous linac sections requiring entire warm-up for repair vs. b) warm breaks between modules for individual warm-up. Operational experience: JLAP, few warm-ups until recently FLASH, only 5 modules, continuous developmental shuffle

10. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 10 ERL Linac Cryogenic Loads Predicted Load Linde and Air Liquide + 50% Margin 1.8K Static/Cavity1 W 1.8K Dynamic/Cavity12 W 1.8K Total/Cavity13 W 1.8K Total Linac (384 cavities)5 kW7.5 kW 5K Static Linac3 kW 5K Dynamic Linac (HOM)6 kW 5K Total Linac9 kW13.5 kW 80K Static Linac7 kW 80K Dynamic Linac (HOM)63 kW 80K Total Linac * 70 kW105 kW * 80K may not be the optimal intermediate temperature Cryogenic load predictions will be tested in the HTC

11. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 11 ERL Linac R&D  Required quadrupole axis alignment, able to share a HGRP with a cavity?  Even vs odd # cavities per module, coupler kick?  Max allowable quadrupole spacing determines # cavities per cryomodule, 6-9.  Cavity cell profile detail (see Matthias)  Center cells for low cryo losses  End cells for HOM propagation  Coupler, lower power (5kW avg), simpler and less cost (see Sergey)  Simplify ERL Injector couplers  Monitor KEK/Toshiba coupler development, modify for adjustability  Lower power IOT, 5kW avg (see Sergey)  Tuner (see Matthias)  Keep INFN blade tuner with piezo modifications?  Monitor/investigate Saclay III?  Simplify and reduce cost of HOM Loads  Use a alternate RF absorbing materials with lower cost  Small circular absorbers soldered to copper plate rather than Elkonite  Little or no e-beam welding  Cryogenic load (see Richard)  Optimize intermediate temperature, presently 80K  40K-120K?  Control optimization, e.g., plumb all 80K and 5K loads in parallel vs. some serialization?  Quadrupole, kickers, and BPM to be designed Items within the Linac Cryomodule requiring development or further investigation

12. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 12 ERL Linac Industrial Role  ACCEL and Meyer Tool have played significant roles for the HTC and Injector  ACCEL: Beamline loads and Technical drawings for Injector cryostat  MTM: Fab HTC and Injector cryovessels, critical review of designs  HOM Loads: simpler design, locate a knowledgeable lower cost vendor  Simplify and reduce cost of couplers: CPI, Toshiba  Lower power IOT: e2v, CPI, Thales, L3, …  Refrigeration plant  Leverage ILC build up. TBD is partition of: cavity chemistry, HPR, vertical test, clean-room assembly, …  AES  Meyer Tool  ACCEL  Zanon

13. August 2-3, 2007 E. Chojnacki, Cornell ERL Director’s Review 13  Single-cavity linac horizontal test cryomodule  Utilize  the Injector HTC cryomodule  proto-type HOM Loads  spare tuner  proto-type couplers  Test  linac cavity HOM Q’s with final shape  microphonics control with high Qext  maybe low power couplers and 5kW avg IOT  Differs from Daresbury test module in higher current and no energy recovery  Proto-type a full ERL linac cryomodule  Industry requires demonstration of performance prior to providing guarantees  Work out bugs ERL Linac Test Modules