# Presentation: 490224

## SMTF Collaboration Meeting

- _SMTF Collaboration Meeting_
- October 5th – 7th, 2005

**Working Group 1**
- Topic 2
- “Updates on HPR, Cleanrooms, and UPW”

- _Speakers:_  John Mammosser (JLab)
- KEK
-                               Detlef Reschke (DESY) - by video?

- _Discussion leaders:_  John Mammosser (JLab)
-                       Allan Rowe (FNAL)

## Philosophical questions (view from above):

_**Philosophical questions (view from above):**_

- Assuming the SRF community adopts the DESY surface processing sequence employed by the XFEL, the following questions should be answered:

- If the XFEL processing program is only able to achieve 28 MV/m reliably, what program of study is required to achieve 35-40MV/m?  *(Waiting for the results from the’final’ XFEL recipe may not be temporally prudent.  The baseline recipe in place now must function as the basis from which improvements can be developed.)*

## Philosophical questions (view from above):

_**Philosophical questions (view from above):**_

- Can a 7-12 MV/m improvement be realized by ‘tweaking’ the XFEL process?
- 	Which recipe steps are the most ‘ripe’ for 	modification?
- 	Which steps are ‘fixed’?

## Philosophical questions (view from above):

_**Philosophical questions (view from above):**_

- Should a beginning-to-end study seeking novel processing ideas be undertaken?
- 	Can this beginning-to-end study be done in the tight-loop testing environment?
- 	What are the main ‘new’ ideas currently in discussion that should be undertaken in a beginning-to-end type study?

## Philosophical questions (view from above):

_**Philosophical questions (view from above):**_

- If the XFEL is able to achieve 35 MV/m reliably with their recipe, should the ILC recipe development focus on cost reduction/processing rate rather than recipe modification to improve gradient?

## What is the particulate count and type added at each process step ?

Is the difference between single cell and multicell cavity performance due to:
Reduced number of hardware ?
Less interaction by personnel ?
Personnel skill ?
Simplicity of structure ?
Surface area ?

- _General Questions_

- What is the particulate count and type added at each process step ?
- Is the difference between single cell and multicell cavity performance due to:
- Reduced number of hardware ?
- Less interaction by personnel ?
- Personnel skill ?
- Simplicity of structure ?
- Surface area ?

## Is there a pattern to field emission location or is it random?

Does the cleanroom particulates cause FE or is it personnel contamination working around them ?

What is the contribution from peripheral components to field emission ?

Does increasing delay from acid removal increase FE onset ?

- _General Questions cont..._

- Is there a pattern to field emission location or is it random?
- Does the cleanroom particulates cause FE or is it personnel contamination working around them ?
- What is the contribution from peripheral components to field emission ?
- Does increasing delay from acid removal increase FE onset ?

## Specific Discussion Questions – In order of process step

- _Specific Discussion Questions_ – In order of process step

_**Post-chemical process rough rinse**__:_

- Are there any objectives to the post-process rough rinse besides removing the remnant salts and acid residue?  Follow-on:  Does UPW alone remove the remnant salts well enough in a low-pressure or flow-through type rinse?
- If UPW is determined to be insufficient to remove residue that can’t be removed by HPR, should an additional fluid besides UPW be introduced into the post-process rinse sequence?

## Post-chemical process rough rinse cont...:

_**Post-chemical process rough rinse cont...:**_

- What type of rough rinsing (flow through & recycled, or flow-through & dump) is most effective?  Follow-on:  What quality of rinse water is required before the cavity can be HPR’d?
- Is this rinse required if the HPR can begin immediately following the chemical process?  (The HPR may sufficiently remove the salts adhered to the surface.)  Follow-on:  If the HPR is pushed through quickly enough in the first couple of passes, will it prevent acid residue from drying on the cavity walls?

## Post-chemical process rough rinse cont...:

_**Post-chemical process rough rinse cont...:**_

- What are the alternative fluids and their benefits?  (H2O2, Isopropyl Alcohol, Ozonated UPW, etc.?)
- Will ultrasonic rinsing remove any particles that the HPR cannot?
- How does elevating the fluid rinse temperature affect the rough rinse?  Follow-on:  What temperature, fluid, and effects can be expected from the hot rinse?

## Post-chemical process rough rinse cont...:

_**Post-chemical process rough rinse cont...:**_

- Due to handling during processing, should the outside of the cavity be rinsed?  Follow-on:  If the outside is rinsed, can it be performed in the same bath as the inside surface rinse?  What contaminants exist on the outside of the cavity that would be problematic for the inside surface if the HPR is to directly follow?

## Cleanroom Handling (rough rinse to HPR):

_**Cleanroom Handling**__ (rough rinse to HPR):_

- How is the post-process rinsing quality verified?  Follow-on:  Can surface analysis be performed, besides the resulting RF test, that shows the results of different rinsing procedures that prove-out a rinse method?
- How long can the cavity ‘dry’ before the HPR rinse begins?  Follow-on:  During the cavity installation on the HPR, what ‘dries’ on the cavity surface and how quickly?  How long can the ‘dried’ contaminant reside on the surface before the HPR will no longer remove it?

## Cleanroom Handling (rough rinse to HPR):

_**Cleanroom Handling**__ (rough rinse to HPR):_

- How long can the cavity sit idly filled with water before the HPR?  Follow-on:  What surface degradation, if any,  occurs with long exposure to water?
- Can particles from the environment (air born, shed from parts, etc.) that ‘stick’ to the wet or drying RF surface during the installation have enough adherence that the HPR cannot remove them?

## High Pressure Rinse:

_**High Pressure Rinse:**_

- What is the characterization of a problematic particle?
- What impinging pressure at the surface is required to dislodge problematic particles?
- Does the water pattern need to be variable so the applied force on the surface comes from multiple directions during the rinse?
- Would a high temperature rinse improve particle removal?

## High Pressure Rinse:

_**High Pressure Rinse:**_

- What is the rinse time (actual exposure to the water spray) required to dislodge problematic particles, especially those strongly adhered.  Follow-on:  Can a longer rinse cycle be substituted for multiple rinses?
- What rinse (drain) water characteristics verify that a cavity is sufficiently rinsed?  Follow-on:  Is a particle count of the rinse (drain) water sufficient to make this verification or would other diagnostics be useful?
- Does the water itself do any damage to the RF surface?  E.g. Stalling the HPR results in localized discoloration on Nb surface.  An etch is required to remove the discoloration.

## High Pressure Rinse:

_**High Pressure Rinse:**_

- How do the alternative cavity shapes (LL, RE), especially for multi-cell cavities, affect the HPR effectiveness?
- Are there alternative technologies that would be as effective as HPR to remove particles from the RF surface?  E.g.  Dry ice cleaning?
- Should the HPR environment be as tightly controlled as the drying environment?

## Ultra Pure Water (production and testing):

_**Ultra Pure Water**__ (production and testing):_

- Which water contaminants increase surface resistance?
- What particulate size and type, if present in the rinse water, causes field emission?
- Is bacteria and/or high TOC (non oil related) really a problem for the RF surface?
- Are the standard water production techniques sufficient for SRF?  (Softener-carbon beds-RO-storage-DI-UV-Ultrafiltration-use)  Follow-on:  Do we require some type of additional treatment (ozonation, etc.) before HPR?

## Ultra Pure Water (production and testing):

_**Ultra Pure Water**__ (production and testing):_

- How have the pharmaceutical/microelectronics industries optimized their water systems so performance is guaranteed on a day-to-day basis?  Follow-on:  What maintenance programs should the SRF community employ to ensure more reliable water production for HPR and other needs?
- What frequency is complete UPW testing (ICP, TOC, Bacteria counts, dissolved solids, etc.) required to ensure UPW is meeting quality specifications?
- Is ultra-filtration before HPR the only requirement for the HPR water source?

## Cleanroom Handling (Cavity drying/storage, vert. test assembly, post-test storage, and cold string installation):

_**Cleanroom Handling**__ (Cavity drying/storage, vert. test assembly, post-test storage, and cold string installation)_:

- Which storage technique (vacuum, class 10 laminar, etc.) provides the least likelihood of particle contamination prior to vertical testing?
- Are there alternatives to bolted flanges that will minimize particle generation?
- Will a final filtered alcohol rinse following HPR speed the drying process enough to limit the air-born particles from sticking to the wet inner cavity surface?

## Cleanroom Handling (Cavity drying/storage, vert. test assembly, post-test storage, and cold string installation):

_**Cleanroom Handling**__ (Cavity drying/storage, vert. test assembly, post-test storage, and cold string installation)_:

- How can one characterize and monitor the potential contamination from vacuum systems used for cavity evacuation, and can this potential contamination be related to field emission in a statistically significant way?