slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
- Motivation - Cleaning mechanism, technique & apparatus - Nb cavity results PowerPoint Presentation
Download Presentation
- Motivation - Cleaning mechanism, technique & apparatus - Nb cavity results

Loading in 2 Seconds...

play fullscreen
1 / 16

- Motivation - Cleaning mechanism, technique & apparatus - Nb cavity results - PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on

Dry-ice (CO 2 -snow) Cleaning. - Motivation - Cleaning mechanism, technique & apparatus - Nb cavity results - Copper rf gun cleaning - Summary, open topics + next steps. Detlef Reschke, Arne Brinkmann IWLC-2010, Oct. 21st, 2010. Motivation for dry-ice cleaning.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '- Motivation - Cleaning mechanism, technique & apparatus - Nb cavity results' - sebastian-mckenzie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Dry-ice (CO2-snow) Cleaning

- Motivation

- Cleaning mechanism, technique & apparatus

- Nb cavity results

- Copper rf gun cleaning

- Summary, open topics + next steps

Detlef Reschke, Arne Brinkmann

IWLC-2010, Oct. 21st, 2010

motivation for dry ice cleaning
Motivation for dry-ice cleaning
  • High cleaning potential for removal of particles + field emission by dry-ice cleaning proven on samples=> publications by Univ. Wuppertal (e.g. SRF Workshops, …)
  • Additional cleaning option:no replacement of high pressure water rinse !
  • advantages of dry-ice cleaning:
    • Effective removal of particulate and film contamination
    • Dry cleaning process=> horizontal cleaning option of Nb cavities=> final cleaning just before string assembly => all applications unsuitable for water e.g. application to Cu gun cavity=> no drying procedure necessary
effect of dic on a flake like emitter courtesy univ wuppertal

emitter

HPR

HPR+DIC

Eon (MV/m)

54.3

62.8



67.4

35.4



51.2

38.0

S (m2)

2 × 10-17

8.3 × 10-13

S (m2)

1.2 × 10-15

2.4 × 10-13

Effect of DIC on a flake-like emitter (courtesy Univ. Wuppertal)

emitter of ~ 20 µm size destroyed by DIC

remnants emitting at higher Eon!

EDX: no foreign element detected

(probably oxide of Nb)

motivation for dry ice cleaning1
Motivation for dry-ice cleaning
  • High cleaning potential for removal of particles + field emission by dry-ice cleaning proven on samples=> publications by Univ. Wuppertal (e.g. SRF Workshops, …)
  • Additional cleaning option:no replacement of high pressure water rinse !
  • advantages of dry-ice cleaning:
    • Effective removal of particulate and film contamination
    • Dry cleaning process=> horizontal cleaning option of Nb cavities=> final cleaning just before string assembly => all applications unsuitable for water e.g. application to Cu gun cavity=> no drying procedure necessary
cleaning mechanism
Cleaning mechanism
  • dry-ice “snow”: mechanical, thermal + chemical cleaning forces- thermo-mechanical: i) embrittling by shock-freezing ii) shearing forces by high momentum iii) drastic volume increase by sublimation- chemical: liquid CO2 acts as solvent for hydrocarbons + silicone=> embrittling, blasting, shearing, dissolving, washing
  • removal of particles down to < 100nm
  • local, dry, without residues
  • simple checks with air and surface particle counters possible
cleaning technique
Cleaning technique
  • patent-registered nozzle design for CO2 surrounded by nitrogen designed by Fraunhofer IPA, Stuttgart, Germany
  • spontaneous formation of snow/gas mixture by relaxation of liquid CO2 - app. 40-45% snow at -78,9°C; ~50-55 bar
  • surrounding supersonic nitrogen gas (20°C; (12-18)bar)=> accelerating + focussing of jet=> (partially) avoidance of condensation of humidity
apparatus general

1

2

3

5

1 valve

2 pressure reducer

3 gas purifier

4 chiller

5 filter

4

5

1

carbon dioxide

nitrogen

Apparatus: General
  • schematic of dry-ice cleaning set-up
apparatus key components operation1
Apparatus: key components + operation
  • system for horizontal cleaning of (1-3)-cell cavities in stable operation
single cell nb cavity results
Single cell Nb cavity results
  • Results with actual cleaning parameters:

=> 3 of 5 tests show no fieldemission up to 35 MV/m; 2 tests with moderate FE

  • Potential to remove HPR resistant field emitters ??
copper rf gun cavity cleaning
Copper rf gun cavity cleaning
  • Task: cleaning of the copper rf gun cavity of the photo injector for FLASH and European XFEL
  • Goal:effective removal of particles => low dark current with no oxidation of Cu

Photo injector area with rfgun cavity at FLASH

copper rf gun cavity cleaning ctd
Copper rf gun cavity cleaning (ctd.)
  • new vertical cleaning stand with modified movable nozzle
copper rf gun cavity cleaning first result
Copper rf gun cavity cleaning: first result
  • three guns cleanedexample: gun cavity 4.2 conditioning at PITZ => dark current during gun processing app. factor 20 reduced
open topics ideas
Open topics + ideas
  • Further optimisation of cleaning parameters:reduced CO2-capillary size, cleaning speed => reduce consumption of CO2 => reduce/avoid moisture condensation => avoid heating ??
  • What is the “better” nozzle head:One movable nozzle vs. two fixed nozzles?(angle of nozzles?)
  • Heating of cavity or inert gas atmosphere ??
  • Improved drive system of cavity
summary outlook
Summary + Outlook
  • In operation:- horizontal cleaning of (1-3) cell cavities => successful

- cleaning of 1.3 GHz Cu gun cavity with movable nozzle => successful

  • Future:- Cleaning of REGAE (Relativistic Electron Gun for Atomic Explorations)

- Regular cleaning of 1.3 GHz gun cavities for FLASH and European XFEL

- Cleaning of water sensitive special parts

  • Options:

- Extension to Nb nine-cell accelerator cavities ?

- Cleaning of full accelerator modules ???