S. Verdú-Andrés, LARP Toohig Fellow Brookhaven National Laboratory CRYOGENIC TEST OF THE PoP DQWCC AT CERN Experience in preparing and cryo-testing the PoP DQWCC at BNL S. Verdú-Andrés, LARP Toohig Fellow Brookhaven National Laboratory

Crab cavities for LHC Crab crossing LHC Crab Cavities Potential benefits from crabs: Luminosity increase Luminosity levelling Alleviate pile-up 2-cavity module SPS test 4 cavities/IP/side/beam Between D2 and Q4 LHC Crab Cavities 𝜃 𝐶 2 Crab crossing reestablish head-on collision for maximal ℒpeak Need 32 crab cavities

Phases of the LHC Crab Cavities project Today SPS Test Final Implementation LHC crab cavity program phases: 2003  2008 Conceptual design, feasibility study and system development 2009  2014 Proof of Principle Cavities 2014  2018 Cavities and Cryomodules for a validation test in the SPS 2017  2023 HL-LHC system

The PoP DQWCC …and stiffening frame Electric field Magnetic field

PoP DQWCC history Bulk and light BCP Light BCP 600°C bake for 10 h BNL - Test II BNL - Test I 120°C bake CERN - Test III Light BCP

BNL insert

Port assembly

Diagnostics for BNL Test II #1 Top TEMPERATURE MONITORING Number: 6 thermosensors Type: CX-1050 Assembly: EPOXY plus kapton tape #5 #4 #2 #1 On top of the upper large port flange (niobium flange) #2 On FPC port pipe #3 On inner ring of cavity dome #4 On PU port pipe #5 On the pipe of the upper small port at the 4-port side (flange with copper disk) #6 On top of the lower large port flange (niobium flange) PU FPC #3 4-port side Vacuum #6 Bottom

Timeline CAVITY PREPARATION (about 2 days) Wipe cavity with ethanol in buffer area and move into class 10,000 cleanroom. The next day, check particle counting. If OK, then wipe cavity with ethanol and move into class 100 cleanroom (ISO 5) The next day, check particle counting. If OK, then cavity ready for opening ports. PORT ASSEMBLY (about 1 day) FPC, PU, particle trap and blank-off flanges in class 100 cleanroom CAVITY ASSEMBLY INTO INSERT (about 1 day) Cavity into insert Connect vacuum line in class 100 cleanroom SLOW PUMPING WITH NEEDLE VALVE (overnigth), TURBO PUMP (half day), LEAK CHECK + RGA, ION PUMP (overnight) Class 100 cleanroom DIAGNOSTICS INSTALLATION (about 1 day) TOP PLATE RIGGING INTO DEWAR AND ROLLING DEWAR INTO TEST BUNKER (about 1 day) CONNECT RF CABLING (CALIBRATION, TIME DOMAIN REFLECTOMETRY) AND CRYO LINE (about 1 day) COOLDOWN TO 4.5K (~) COOLDOWN TO 2.0K (~) TEST (about 3 days)

Measurements and Results Q0 at around 3~4.5e9. In CW mode, temperature of beam pipe flanges increase. Reached 4.5MV kick in pulsed mode, limited by quench, consistent with conditioning test. Temperature increase on pickup port blending area. Quench field at ~110mT, with peak E field at 52.8MV/m 𝑅 𝑟𝑒𝑠 : ~18.3nΩ

Measurements and Results Lorentz detuning (df/dVdefl)  freq = f(V) -206 Hz/(MV)^2 from CW measurement at 2K Pressure sensitivity (dp(=dT)/df)  freq = f(Tbath=p) -336 Hz/Torr from low power measurement during cooldown from 4.2K to 2K

Measurements and Results Residual surface resistance 𝑅 𝑟𝑒𝑠 : ~18.3nΩ

Cavity status BNL cadeau arrives at CERN on July 10, 2014 PoP DQWCC and its stiffening frame in bldg 252-R-003 now Sealed with stainless-steel flanges* after light BCP at Argonne in May 2014. Cavity is equipped with its own stiffening frame. * BNL property, to be shipped back to BNL inside transportation box.

PoP DQWCC test at CERN - objectives CERN Test III PoP DQWCC test at CERN - objectives Test all the candidate crab cavities on the same baseline. Prepare CERN test facility for future SPS cavity tests. Quench in Nb-coated DN100CF flanges? Freshly Nb-coated flanges may lead to better performances. Plus evaluate technology for SPS DQWCC e.g. tuning system

Test program for PoP DQWCC at CERN CERN Test III Test program for PoP DQWCC at CERN 1st – fixed FPC (vertical test) 2nd – movable FPC (vertical test) 3rd – SPS tuning system (horizontal test) Fixed FPC (bolts) CERN FPC actuator based on BNL design CERN Insert Type I

Cavity assembly - ports CERN Test III Cavity assembly - ports # FUNCTION CONNECTION A blank-off solid DN100 – non-standard port B FPC FPC actuator system C solid DN40 D E PU PU feedthru DN40 F vacuum DN10040 and valve G H

Clean assembly – BNL class 100 cleanroom Stiffening frame wrapped in plastic to reduce contamination Port assembly on wire table

CERN Insert – SPL type Bottom plate a’ la SPL  leak test in cleanroom CERN Insert Type SPL Bottom plate a’ la SPL  leak test in cleanroom

Fixed FPC - bellow length for critical coupling? Facts: Critical coupling (b=1) depends on: Q0, given by cavity performance Qext, given by FPC settings Impossible to predict Q0 beforehand Overcoupled (b>1) structure preferred as lower power requirement Strategy: From 2nd cryo test at BNL, Q0 ~ 4e9. After light BCP at ANL, better performances expected: Q0 > 4e9. b=>1  Qext slightly lower than expected Q0. e.g. set Qext = 4e9 -> d’=21.2mm bellow length The FPC is set at 21.2mm away from the cavity inner surface to the FPC tip, with a Qext at 4e9. If you want to change Qext to 1e10, the distance will be 25mm. Tuesday, Sept 23 (S. Belomestnykh) As the FPC is not adjustable, set Qext somewhat lower, 3e9 or 2e9, to help conditioning the cavity.  Bellow length ~ 27mm. Remarks: FPC coupling depends on coupler shape, penetration and orientation.  Pay special attention during assembly to the coupler orientation.

FPC coupler orientation for fixed FPC

Diagnostics – 6 CERNOX CX old PU CX Inner radius of cavity dome (highest E-field)? Or outer radius of cavity dome… (high B-field) FPC Inner radius of cavity dome (highest B-field) CX CX PU CX Vacuum heater Other thermosensors in all these regions plus in old and new pick up ports and, if possible, in all ports (on blended area of cavity and port plus on flange) CX

Diagnostics – OSTs Possible quenching regions: FPC PU Possible quenching regions: beam ports plate Possible quenching regions: Cavity dome FPC PU plate Vacuum

Diagnostics – 3 unidirectional fluxmeters

Measurements to be performed CERN Test III Measurements to be performed Monitor vacuum level, radiation (field emission and multipacting) during operation at different field levels Q slope (i.e. Q=f(V)) at 4K and 2K Q = f(T) for low field level to get residual surface resistance estimation Residual magnetic field level and corresponding residual magnetic field surface resistance Lorentz force detuning (df/dVdefl)  freq = f(V) Pressure sensitivity (dp(=dT)/df)  freq = f(Tbath=p) Determine multipacting regions. Radiation spectra Magnetic field

Cavity far from ideal… heat loss CERN Test III Cavity far from ideal… heat loss FPC bellow is not coated (difficult to coat welded flanges). Spacing between flanges will let field see SS from flanges and Cu from gasket. FPC and PU hooks made of copper (Nb coating was not adherent enough on copper surface).

Thanks for your attention Questions?

Cavity assembly – hardware (I) PORT FUNCTION CONNECTION BOLT TYPE #BOLTS #NUTS #WASHERS A blank-off solid DN100 M8x55 x16 x32 B FPC system bellow DN40 M6x35 x4 x8 anti-collapse ??? feedthru DN40 C solid DN40 x6 x12 D E PU F Vacuum: DN10040 and valve DN10040 valve DN40 G H In addition, bolts and ¿pins? for stiffening frame in case of magnetic hardware is found hardware for the piece on top of the cavity for transportation

Cavity assembly – hardware (II) BOLT TYPE # BOLTS # NUTS # WASHERS M8x55 32 64 M6x35 48 44 88 Anti-collapse? 4 16 8 Total DN40 copper gaskets: 8 Total DN100 copper gaskets: 2 Remarks: all bolts are Ag-coated A4-100 stainless-steel apply safety factor of 2--3 when ordering

Cavity assembly – FPC system Two options: Fixed FPC: 1st test Movable FPC: 2nd test Remarks: FPC coupling depends on coupler shape, penetration and orientation.  Pay special attention during assembly to the coupler orientation.

FPC actuator T. Renaglia (CERN) based on BNL design

Framework – LHC Crab Cavities If head-on collisions, debris can interact with the machine Crossing angle but decreased peak luminosity 𝜃 𝐶 2 𝜃 𝐶 2 Crab crossing reestablish head-on collision for maximal ℒpeak Need crab cavities (deflecting cavities in phase 0) For LHC, need 4 cavities per side per IP per beam… 32 cavities!!!