with the contributions of my colleagues from BI and CRG Status of the AD’s CCC Jocelyn TAN (BE-BI) with the contributions of my colleagues from BI and CRG GSI visit at CERN

Agenda Recap on the AD’s CCC Cryolab activities : maintenance, R&D Plans

AD CCC Vacuum tank Thermal shield 840 LHe Vessel Nb shielding 1032 Safety valves Pulse tube + He hose Vacuum tank Instrumentation + vacuum equip. Thermal shield 840 LHe Vessel Nb shielding 1032 Courtesy: A. Lees TE-CRG

AD CCC status before LS2 Status Limitations Current and intensity measurement provided at end of cycle: resolution of 105 charges Very good immunity to mechanical vibrations Fully integrated in FESA (including automatic SQUID set-up) Expert GUI has been developed PLC system available to control cryogenic system Limitations Cryogenic availability : refill every 2.5 months LHe circuit becomes contaminated blocking the He gas flow in the closed-circuit: CCC could nevertheless work w/ GHe, up to ~ 7K. Measurement display only possible at end of cycle Due flux-jump at injection Tested: battery power, isolation amplifiers, better calibration cable, … Superconducting connection in DC coupling circuit kept only for limited range Currently compensated by imposing a constant DC current

AD CCC status before LS2 Successful run in 2018 with similar problems of LHe reliquefaction (refill every 2.5 month) Upgraded reliquefier performance 0.89 W + 0.32 W = 1.21 Wequiv. did not help! No further performance tests possible due to cut of supplies end of 2018 until march 2019 Installed 2 x PV in pumping line protected vacuum from oil back stream (power cut) Courtesy: T. Koettig TE-CRG

Investigation of performance degradation Possible options for performance degradation were identified: Diffusion of He through the ceramic gap and local influence of insulation vacuum mainly around the beam tube (30 MlI layers and little space) => excluded by an extensive leak test in May 2019 with 1 bar GHe @ 293 K in the inner LHe vessel => Q 𝐿 <3∙ 10 −9 mbar l/s insulation vacuum to leak detector Liquid helium vessel inner bore assembly. Configuration for integration into the BCCCA. Cryostat insulation vacuum LHe or GHe Ceramic gap setup for leak testing before installation. 3 axial mechanical support rods! Test pressure 1.5 bara x 1.25 = 1.875 bar differential. Courtesy: T. Koettig TE-CRG

Investigation of performance degradation Possible options for performance degradation were identified: Diffusion of He through the ceramic gap and local reduction of insulation vacuum mainly around the beam tube GHe impurities due to supply or air diffusion etc. creating layer on 2nd stage HEX Independent GHe supply (not anymore from the central building supply 46 He) Courtesy: T. Koettig TE-CRG

Investigation of performance degradation Possible options for performance degradation were identified: Diffusion of He through the ceramic gap and local reduction of insulation vacuum mainly around the beam tube GHe impurities due to supply or air diffusion etc. creating layer on 2nd stage HEX => 2 x SV are under suspicion to be not backwards leak-tight => Full metal SV for cryogenic use! => Plan is to replace it with a combination of a RD and a bleeding valve. Metal sealed SV at 0.5 barg Rupture disk @ 0.5 barg + bleeding valve @ 0.4 barg, O-ring sealed Courtesy: T. Koettig TE-CRG

Maintenance plan Maintenance kit for the compressor unit is purchased. Run time is already (~22000 h) for compressor CP1110 with PT415 => CP1110 Molecular Sieve Adsorber, CRYOMECH Description 1 97-20 CP1110 Courtesy: T. Koettig TE-CRG

R&D on remote cooling scheme Working principle: Use cryocooler with closed helium circuit to deliver cooling power to remote cryostat Heat exchangers are crucial component Forced flow of helium gas (or 2-phase flow) Use cold Joule-Thomson expansion valve for temperature reduction Project goals from cryo perspective: Increased flexibility in coolling options for different projects; Reduce dependency on LHe availability Possibility of placing cryocooler away from locations of high radioactivity and magnetic field Dry cooling and gas cooling options possible Dry cooling He gas Gas cooling Status and plans: Currently assessing performance of heat exchanger with coolling circuit connected only to first-stage of cryocooler Total expected development for a production system of 3 to 4 years With 2 last years of specific design for any given system

Advantages/changes for a future CCC Cooling pipe with dry cooling option: no helium vessel is required Smaller and cheaper cryostat design No ceramic gap in contact with liquid helium Strong pressure changes perturbations eliminated Temperature stability Should not be an issue with core-less CCC Maybe require an active temperature control Vibrations from active gas flow Impact should be mitigated with core-less CCC Use single-phase gas flow To be investigated

Next steps for AD Study source of flux-jump at injection Re-measure system response, and assess maximum achievable slew-rate Replace Magnicon “Connector box” and “Power supply” by improved electronics, to be installed in a single box Mitigate perturbations through signal processing Install new B-train / “White Rabbit” receiver (same system as for DCCT’s)

Next steps for ELENA There is interest to have a CCC in ELENA Some pre-requisites though: Show that AD CCC can run reliably over long periods; Wait until ELENA is fully commissioned; If it is shown that intensity measurement is lacking, then we can proceed with an optimised design for an ELENA CCC ; Timeline: not before the end of 2021 at the earliest.

Next steps for the collaboration Cryogenics: FAIR cryostat, new cooling scheme SQUID: new design; outcome on rad hard tests New CCC design: coreless ? Lead? To be presented this Thursday at FCC week Courtesy: T. Dodington BE-BI

Thank you

Spare Slides

ELENA for experiment efficiency improvement Factors considered in the synchrotron design Space constraints: in AD hall e-cooler: get space + small dispersion Tune: keep  away from resonances Bucket to bucket beam transfer from AD Possibility of a second extraction line ELENA parameters Circumference (1/6 of AD) 30.4m Triplet-based optics 6-fold layout Machine tunes h/v 2.3 / 1.3 Ekin range 5.3 MeV – 100 keV Relativistic  0.11 – 0.01 Nbunches at extraction 4 Bunch length at extraction 75 ns (rms)

Facility overview and layout Transfer line (magnetic)from AD External source for commissioning Electro-static line towards existing experimental area Extraction towards new experimental area Courtesy: C. Carli

ELENA Cycle Cycle length about 20 seconds ELENA parameters Ekin range 5.3 MeV – 100 keV Frev 1.1 MHz – 100 kHz Total Nparticles 3 – 1.8 x 107 DC current range 5.2… 0.3 A Beam aperture 63 mm eh,v = 15 p mm mrad DP/P = 1x10-3 eh,v [95%]= 6/4 p mm mrad DP/P = 2x10-4 Lbunch (max) = 1.3 m Cycle length about 20 seconds

in Section 1: near septum and kicker Integration options 1.25m drift tube in Section 1: near septum and kicker LPUs in Section 2