Mini-workshop on beam-line field-emitter particulates in CEBAF SRF linacs

Monday Feb 29, 2016, 9:00 AM → 4:01 PM US/Eastern

TL1227 (Test Lab)

Rong-Li Geng (Thomas Jefferson National Accelerator Facility)

Goal: Evaluate field-emission impact to operation of CEBAF SRF linacs. Identify the root cause(s) of particulate field-emitters in operational SRF cavities, with a focus on the particulates originating from the UHV beam-line components. Develop solutions for “particulate-free” beam-line components for future SRF linacs as well as mitigations against accumulated field emitter particulates for operational SRF linacs. Topics: • Observations and experiences with beam-line particulates and correlation with field-emission. • Sources of particulates in UHV beam-line components. • Roles of condensed residual gases. • Mechanisms of particulate transportation in UHV beam-lines. • UHV beam-line component design for lowest particulate generation. • UHV beam-line component cleaning, handling, assembly and operation procedure for lowest particulate generation. • Mitigation against field-emitter particulate in operational SRF linacs. • Techniques for removal of accumulated field emission particulates. • UHV beam line-particulate detection technique. • Fast detectors for in operando monitoring of field-emission turn on. Program committee: Rongli Geng (Chair), SRF R&D, AD Arne Freyberger, CEBAF Operation, AD Geoff Krafft, CASA/AD office, AD Tim Michalski, Mechanical Engineering, ED Tony Reilly, SRF Operation, AD

1 Aim of the workshop

Speaker: Dr Rong-Li Geng (Thomas Jefferson National Accelerator Facility)

Slides Workshop_Aim.pptx

2 Technical and economical motivation

Speaker: Arne Freyberger (JLAB-Accelerator Division-Operations Department)

Slides FieldEmissionWorkshop.pdf

3 FE experiences with C100 module operation

Speakers: Clyde Mounts (EESRFS), Mr Rama Bachimanchi (Jefferson Lab)

Slides mini_WS_Bachimanchi_CIM.pptx

4 Evolution of FE characteristics of selected modules

Speaker: Mr Michael Drury (Jefferson :Lab)

Slides FE_Evolution.pptx

Review of current practices

Review of current practices in cavity string assembly, cryomodule installation, warm girder UHV components installation/maitenance. Give special attention to designs/procedures aimed for minimizing particulate generation/transportation.

5 C100 cavity string assembly

Speaker: Kurt Macha (Jefferson Lab)

Slides mini_WS_Macha.pptx

6 Cryomodule installation in CEBAF tunnel

Speaker: John Fischer (Jefferson Lab)

Slides mini_WS_Fischer.pptx

7 Warm girder UHV components

Speakers: Anthony DiPette (Jefferson Lab), John Hechman (Jefferson Lab)

Slides Warm_Girder_UHV_Comp.pptx

12:00 PM Lunch (on your own)

Panel discussion

Panelist: Anthony Dipette, John Fischer, John Heckman, Kurt Macha

Convener: Dr Rong-Li Geng (Thomas Jefferson National Accelerator Facility)

8 LCLS-II cryomodule installation planning

Speaker: Dr Chris Adolphsen (SLAC)

Slides Issue_of_Particle_Free_Collab_Mtg_20150605.pptx mini_WS_LCLS2.pdf

Brainstorm action list

• Near term actionable items to slow down FE particulate generation
• Particulate-free UHV component design for SRF linacs

Conveners: Anthony Reilly (JLAB), Tim Michalski (Jefferson Lab)

9 NEG pumps

Speaker: Marcy Stutzman (Jefferson Lab)

Slides NEG_pumps,_bemline_FE_workshop.pptx

Brainstorm action list

• Future on-line and off-line testing
• Future studies on particulate transportation e-beams
• Long term implementable mitigations

Convener: Geoff Krafft (JLab)

slides Mini_WS_Krafft.ppt

10 Closeout

Speaker: Dr Rong-Li Geng (Thomas Jefferson National Accelerator Facility)

Adjourn