Summary of the Mini-Workshop on cavity R&D

Haus Rissen, Feb 28th, 2002

 

 

Participants

 

FDET:           A. Knabbe, L. Lilje, P. Schmüser, B. Steffen

MHF-SL:        A. Brinkmann, D. Kostin, W.-D. Möller, D. Proch, D. Reschke

MKS:            D. Gall, R. Lange, A. Matheisen, D. Sellmann, N. Steinhau-Kühl, S. Wolff

MPL:            W. Singer

MVA:           J. Tiessen

MVP:            K. Zapfe

 

Introduction

 

The results and important statements of the one-day mini-workshop on cavity R&D on single-cell Nb cavities are summarised briefly.

The presented transparencies are attached in the appendix.

 

Program:

 

I)               status and results of single-cell cavities:

-       EP- and BCP cavities (L. Lilje)                                             

-       Tumbled cavities and Palmieri Spun Cavities   (D. Reschke)                   

-       New suppliers for cavity material (D. Proch)                           

-       Hydroformed Cavities and material studies (W. Singer)                        

 

II)              INFRASTRUCTURE:

-       BCP and EP in hall3 (A. Matheisen)                                       

-       EP at CERN (L. Lilje) (no transparencies)                                

-       EB-welding and cavity fabrication at DESY (J. Tiessen)                       

-       Test infrastructure at hall 3 (R. Lange)                 

-       Test infrastructure at Petra hall NO (CTA) (D. Sellmann)              

-       Tests at other labs (L. Lilje) (no transparencies)                               

 

FIRST SUMMARY of cavities (existing and under construction), number of cold tests and cavity preparations in 2001 (D. Reschke)                                                

               

III)             FUTURE R & D:

-       R&D on EP and baking at (100 – 150) C (L. Lilje)                       

-       R&D on tumbling (D. Reschke)                                            

-       R&D on hydroforming and niobium material (W. Singer)                        

-       Nb films on saphire and calculations on Lorentz force detuning (A. Knabbe)

-       Magnetic properties of niobium sample (B. Steffen)                   

-       R&D and commissioning of the DESY EP facility (N. Steinhau-Kühl) 

 

 

IV)           DISCUSSION :

-       Discussion of proposed activities (no transparencies)                                 

-       Priority and schedule of future cavity preparation and testing        (see below) 

 

 

Topics of the discussion and open questions:

 

New single-cell cavities, new materials:

- Qualification of new (old) suppliers: Cabot, Giredmet, CBMM, H.C. Starck => high RRR material, various Ta content of Nb

- Nb material (Wah Chang, Heraeus) for new single-cells available

- Commissioning of DESY EB welding (under progress) => optimisation of welding parameters for highest gradients (starting April 02);

  first single-cells in August 02

- Improved  metallurgical analysis at DESY under commissioning

 

EP-cavities:

- Average gradient of EP single-cells is 35 MV/m, but wide scatter between (30 – 43) MV/m
  => Reproducibility of gradient

- Why is EP better than BCP? => only surface roughness?

- Necessity of 1400C titanisation?

- Horizontal EP does not result in H contamination => Parameters to avoid H contamination!

- Commissioning of DESY EP installation (starting in May 02; see below)

 

100C Baking:

- necessary for best cavity performance (EP + BCP)

- Optimisation of best parameters necessary

- High field effect of baking not understood (Anodising, sample investigations)

- Influence of storage under air and N2 on the cavity performance?

 

Multipacting:

- EP cavities show stronger MP than BCP cavities

- mechanism of x-ray burst during quench not understood

- degradation of Q-value during MP processing due to frozen-in-flux is pausible, but final proof missing (role of adsorbed gases?)

-  Is there another MP level at (30 – 35) MV/m ? (addendum of the editor)

 

Alternative cavity production and preparation

 

Spinning:

- single-cells achieve up to 39 MV/m after EP + bake

- problem of uniform wall thickness + high surface roughness

- 6 new single-cells at DESY; more 1-cells +  3-cells under preparation

 

Hydroforming of Nb:

- single-cells achieve up to 42 MV/m after EP + bake

- problem of high surface roughness

- 2-cells + 3-cells under preparation (beginning of 2003)

 

Hydroforming of NbCu

- problems with Nb-Cu contact + uniform wall thickness at iris region

- wide scatter of cavity performance => optimisation of parameters necessary

 

Tumbling:

- removal of the “damage layer” by tumbling

- first 2 single-cells show promising results => new test after EP under preparation

- How much BCP/EP is necessary to remove residues of tumbling material?

 

Preparation infrastructure:

- no parallel EP and BCP at hall 3 possible => weekly changing

- start of EP with “standard” CERN/KEK parameters

- fast change from single-cell cavities (2-3 tests) to nine-cell cavities

- conflict of KEK EP 9-cells « DESY EP 9-cells « preparation of module 2* « single-cell EP

- second baking apparatus required, but no man power available (MKS, MVP, ZM)

- EP at Fa. Henkel: contacts to experienced EP company with the goal of a “commercial” single-cell EP

 

Test infrastructure à Hall3:

- ca. 27.4. – 27.5. 02 no vertical tests possible (warm-up of LINAC)

- mid of June for 2 weeks no vertical test possible

- Up to 3 (-4) tests per week possible

- CTA at Petra hall NO: one single-cell test per week possible

à Other labs (CERN, Saclay):

no tests possible (except few tests of hydroformed cavities at Jlab)

Priority of activities

NOTE:

The mentioned priorities are “absolute” priorities independent of the time schedule or delays.

Example: As the topics “Qualification of the HPR system” with priority 1 and “Qualification of the EP at DESY” with priority 2

will start not before April 02 and June 02, respectively, cavities of the topics “EP treatment at CERN” with priority 3 will be tested.

 

The proposed 100°C Bake-out inside the cleanroom furnace  (titanisation furnace) is technically not possible and therefore skipped.

 

Priority

Activity

Start date

No. of existing /new cavities

No. of tests

 

 

 

 

 

1

Re-qualification of the HPR system at hall 3

End of April 02

2/-

2

2

Qualification of EP at DESY

June 02

3/-

Up to 6

3

Standard EP at CERN
(last preparation)

Under way

4/-

Up to 8

4

Venting and storage at air and N2

Immediately

2/-

Ca. 8

5

Cavities of new NB suppliers + qualification of EB-welding at DESY

August 02

-/ca 18

Ca 18-21

5 ctd.

Spun cavities

?

6/-

>6

6

Anodizing + Oxipolishing

Immediately

2/-

Ca 16

7

Parameter check of 100°C bake-out

Immediately

5/-

Ca 15

8

Tumbled cavities (partially identical with “3”)

Immediately

2/-

2 after bake-out

8 ctd.

Tumbled cavities

End of 02

-/2

2 after bake-out

 

 

 

 

 

 

EP + 1400°C

Immediately

 

 

 

Low RRR-cavities

Immediately

3/-

3-6

 

Hydroformed Nb cavities

Beginning of 03

-/4

Test at Jlab/KEK

 

Hydroformed NbCu cavities

mid of 02

-/3

Test at Jlab/KEK