SRF DEVELOPMENT AT DARESBURY LABORATORY A. Wheelhouse ASTeC, STFC Daresbury Laboratory 2 nd PASI Workshop, RAL 3 rd – 5 th April 2013

SRF DEVELOPMENT AT DARESBURY LABORATORY

A. WheelhouseASTeC, STFC Daresbury Laboratory

2nd PASI Workshop, RAL 3rd – 5th April 2013

Outline

• Mini PIPSS / IPS Programme– Aims & Objectives– Progress & Results

• SRF Cryomodule Development– Aims & Objectives– Progress

• Summary

4th April 2013 PASI Workshop A Wheelhouse

Mini PIPSS & IPS Programme


Aims


• The fundamental remit of the Mini PIPSS & IPS, Industry Partnership Schemes is to develop the capability of UK industry in the manufacturing of superconducting RF cavities

• Mini PIPSS– Fabrication of a single cell niobium cavity (1-year)

• IPS– Fabrication of a bulk niobium 9-cell accelerating structure (3-year)

• Cell to cell alignment• Tuning robustness and uniformity• Tolerance management• Cleaning/processing compliance • RF surface integrity management

• Technology directly applicable to future large scale accelerator facilities. Opportunity for Daresbury Laboratory and Shakespeare Engineering Ltd to

develop unique capabilities in the UK Enable Shakespeare Engineering Ltd to exploit the large SRF commercial

opportunity

Objectives


• Mini PIPSS– Fabrication of a single cell TESLA SRF cavity– Acceleration gradient > 15 MV/m at a Qo better than 1 x 1010

• IPS– Fabrication of a 9-cell TESLA SRF cavity which will be qualified in 2 ways:-– Accelerating gradient > 20 MV/m at a Qo better than 1 x 1010 after

conventional Buffer Chemical Polishing (BCP) is performed– Accelerating gradient > 30 MV/m at a Qo better than 1 x 1010 when Electro-

Polishing (EP) chemical processing is performed

Aim to provide a clear indication of Shakespeare’s capability and assist in qualifying them as a potential supplier

Cell and Beampipe Forming• Cavity half cells and beampipes fabricated by

Shakespeare Engineering • Half cells pressed on a 60 t hydraulic press

– Pressing performed in 3 operations

• Beampipes were spun using a CNC spinning machine– Eliminates additional welded seam joint– Spinning of cones performed with intermediate

heat-treatments – Beam tube finally formed on a mandrel

3 single cell cavities welded at JLab


PIPSS #01 (JLab)


Multipactor

Target

• Achieved 15.7 MV/m with a Q0 of 1.15 x 1010

• CW and pulsed conditioning

• Gradient - 17.6 MV/m with a Q0 of 2.17 x 109

PIPSS #01 (JLab)


• Additional BCP etch − Approximately 41µm removed

PIPSS #01 (JLab)


• Vac furnace run at 600ºC for 10 hours• Plus an additional BCP etch

− Approximately 28µm removed− Further high pressure rinses

PIPSS #01 (JLab)


• Further high pressure rinses

PIPSS #02 (Daresbury)


• Acid fume cupboard used to perform the BCP etch• Thickness removed measured on a sample piece

which doubled as a stirrer• Acid temperature monitored 85µm removed in 2 etch runs

– Cavity turned up the other way for the 2nd run• HPR performed for 1 hour• Cavity sealed in a ISO4 class cleanroom

PIPSS #02 Evaluation


• VTF manually filled from a 1000lt dewar

• Reduced performance achieved on second cavity processed at DL

Ineffective temperature control on the BCP etch

• Improvements to BCP processing is underway– Further testing to be performed

PIPSS #03 (FNAL)

• EB weld good– Some inclusions

EB weld inspection

Electro-polishing monitoring


Electro-polish - 150µm

Ultrasonic Clean

High Pressure Rinse

Vacuum Bake - 800ºC 2 hrs, <5x10-07 mBar

Electro-polish - 30µm

Ultrasonic Clean and Rinse

High Pressure Rinse

Vertical Test Assembly

High Pressure Rinse

Slow evacuation and leak check

Vacuum Bake - 120ºC 2 hrs, <5x10-07 mBar

Vertical Test

FERMI Lab Standard Preparation

PIPSS #03 TestsFermiLab Tests• Cavity tested at 2K• Maximum accelerating gradient 25 MV/m with Q0=1.5x1010

• Gradient limited by a quench– First quench at 18 MV/m– Quenched twice at 21 MV/m– Finally quenched at 25 MV/m– Limited by repetitive quenches at 25 MV/m which showed no sign of

conditioning after 20 mins• No field emission above background was observed • Some multipacting was noted at around 18 MV/m

– Instabilities in Ptransmitted signal were observed

– Common ILC-shape multipacting range – Multipacting processed

Successfully met target


PIPSS #03 Tests


Target

PIPSS #03 - Further Qualification


CBP

• Further processing performed• Cavity has been CBP

– Removing ~180µm• Light 30µm electro-polish to remove

a weld inclusion• Vacuum bake at 800ºC• Cavity to be tested 5/4/13

Typical before and after CBP

IPS Programme• 3-year programme on-going• Cavity drawings complete• Tooling has been manufactured• Pressing trials being completed with

Copper– Assessing repeatability and

reproducibility Niobium half cells to be pressed soon• Further beampipe spinning trials

– Thicker sheets• SRF infrastructure development

– Automated BCP process– Automated HPR

• It is hoped that FNAL can continue to assist in qualifying Shakespeare with this structure.

9-cell cavity drawings

BCP facility HPR stand


ALICE

SRF Cryomodule Development


http://zms.desy.de/index_ger.html

http://www.hzdr.de/

http://www.triumf.ca/

Aims & Objectives• To lead the design of a new, high current and

world leading cryomodule.• To educate and demonstrate effective:

– Processing, – Handling, – Assembly,– Testing,– QA processes.

• To integrate the new cryomodule onto ALICE• Commission cryomodule + cryogenics systems• To validate cryomodule performance with beam


SRF Cryomodule

Existing Cryomodule on ALICE

ERL (New) Cryomodule

• International collaboration initiated in early 2006:– ASTeC (STFC)– Cornell University– DESY– FZD-Rossendorf– LBNL– Stanford University– TRIUMF (2009)

• Fabricate new cryomodule and validate with beam.

• Dimensioned to fit on ALICE:– Same CM footprint– Same cryo/RF interconnects– ‘Plug Compatible’


SRF Cryomodule

Existing Cryomodule on ALICE

ERL (New) Cryomodule


Parameter ALICE Target

Frequency (GHz) 1.3 1.3

Number of cavities 2 2

Number of Cells per Cavity

9 7

Cavity Length (m) 1.038 0.807

Cryomodule Length (m) 3.6 3.6

R/Q (Ω) 1036 762

Eacc (MV/m) 12 - 15 >20

CM Energy Gain (MeV) 27 >32

Qo <5 x109 >1x1010

Qext 4 x 106 4x106 - 108

Max Cavity Fwd Power (kW)

10 SW 20 SW

Coupler Conditioning• High power conditioning of

the CPI input couplers:– Up to 30 kW (pulsed)– Up to 10 kW (CW)

• For these tests, couplers water/air cooled only

• No vacuum activity seen

Pulsed Conditioning


Coupler Conditioning• High power conditioning of

the CPI input couplers:– Up to 30 kW (pulsed)– Up to 10 kW (CW)

• For these tests, couplers water/air cooled only

• No vacuum activity seen

CW Conditioning


Cryomodule Assembly


HOM assembly

µ metal installation

Cavity string

Cavity wiring

Cold Tests (Off-line)• Check the cryogenic performance • Understand the processes and establish

commissioning and operating procedures • Validate instrumentation• Cavity frequency verification

• Issue with tuner sticking had to be resolved

• Identify and resolve any unknown issues• 80K tests successfully completed• Attempted to cool-down to 4K however:

• Large temperature gradient between the two cavities• Helium reservoirs did not fill completely

• Result of blockage between cavity bottom fill connection and excessive heat load at the input transfer line


Parameters Measured Specification

Static Heat Load at 80K ~ 7 W 20W

Static heat losses for the cavities at 80K

~ 3.5 W 15 W at 4K

Delta T across thermal shield at equilibrium

< 5K <10K

Delta T across the two cavities during cool-down

< 5K< 5K

Currently 50-60K for ALICE

Cryomodule Evaluation• Cryomodule installed and cooled to 2K• Optimisation presently being performed on the

cryogenic system

Evaluation Programme:-• Establish gradient and Q0

• Measure Lorentz force detuning at high gradient • Performance measurements with piezo tuners • Determine DLLRF control limitations wrt Qext

• Evaluate the effect of beam loading with DLLRF, piezo control for various Qext levels under pulsed and CW conditions

• Characterise cavities in CW mode at high gradient:– Evaluate thermal transients across cavity string and

2-phase line

• Synergies with PXIE operational requirements to be evaluated

Cryomodule installed on ALICE


Summary Verified the fabrication of a single cell SRF cavity 9-cell SRF cavity and infrastructure development

progressing UK SRF capability in a stronger position thanks to

FNAL collaboration

Cavity string integrated into the cryomodule Cryogenically commissioned cryomodule off-line Cryomodule now installed in ALICE Cryomodule characterisation about to commence


Documents

SRF DEVELOPMENT AT DARESBURY LABORATORY A. Wheelhouse ASTeC, STFC Daresbury Laboratory 2 nd PASI Workshop, RAL 3 rd – 5 th April 2013