Update on Cryotarget System Jian-ping Chen GMn Collaboration Meeting, Feb. 24, 2014  Overview  Maintenance/Modifications During Down  Installation Status  Target Operator Training

Overview  Standard Configuration: 3 cryogenic loops + solid target ladder Each loop can be used for one of the following cryotargets with variable target length (nominal 15 cm) 1) LH2: Liquid 19 K, ~25 psi 2) LD2: Liquid 22 K, ~22 psi 3) He: Gaseous helium at low T (~7K) high P (~200 psi) Solid targets dummy (aluminum foils for study window contribution) multi-foil optics target up to 7 (limited by lifter travel distance) foil-targets (user specify)

GMp/DVCS Configuration  Only 15 cm LH2 for all loops  Use large 3-in CF cell improved flow design reduce density fluctuation  Large vertical acceptance requirement for DVCS (~20 degrees)  Two loops in March, add 3 rd loop from Silviu Covrig’s design in Fall  Solid targets (less than 2% radiation length for March running) Standard dummy target Standard optics target 5 foil targets (including hole 12C target and BeO) Empty  Special pointing wire target

Target Cells/Cell Blocks

Maintenance & Modifications During Down Improve reliability and performance Make interchangeable with Hall C cryotarget Increase safety INSIDE THE SCATTERING CHAMBER 1)New plumbing between cells and heat exchangers, matches Hall C (complete); 2)New thermometers, all cernox (complete); 3)Vapor pressure bulbs removed (complete); 4)New, heavier wiring to match Hall C cryotarget (in progress); 5)New, easy to replace high power heaters, similar to Hall C (complete); 6)New, more reproducible alignment device to match Hall C (complete); 7)Improve pressure relief path (complete); 8)Rebuilt LH2 pumps (complete); 9)Higher performance cells, flow diverters, and cell blocks (in progress). C. Keith/D. Meekins, Dec. 2013

General Maintenance & Modifications OUTSIDE THE SCATTERING CHAMBER 1)New, higher-power heater supplies match Hall C (complete); 2)ITC501/502 temperature readouts replaced with LakeShore 218 (complete); 3)New cables between electronics and target, matches Hall C (in progress); 4)Solenoid valves removed from gas panels (complete); 5)All safety reliefs replaced with ASME-approved reliefs (in progress); 6)JT-valve controllers modified to reduce readback noise (complete); 7)Pump/purge panel for VP bulbs removed (complete). SOFTWARE 1)Upgraded to current version of EPICS (complete); 2)Control GUI upgraded from MEDM to EDM (accelerator standard) (complete); 3)CAD Drawings updated (in progress);

Current Status: TARGET INSTALLATION STATUS: 1)Cryotarget transported to Hall A last Wednesday (2/19). 2)Cellblocks installed/connected Friday (2/21). 3)Lifting into scattering chamber today (2/24), connecting plumbing. 4)H2/D2 tanks refurbished, back in place. Connections complete this week (2/28). 5)Auxiliary heater controls/temperature readback in CH 1 st week in March (3/7). 6)3” cells: both leak. New cells (thicker walls) arrive in one week, testing, installation follows. 7)Alignment was on 2/27, postponed. New date to be determined. 8)New remotely-adjustable camera to monitor critical readbacks, ready by 3/7. 9)Wire target parts complete, needs assembly. TOSP wait for approval. Schedule is tight, but still on track for March 10 cooldown. C. Keith/D. Meekins, Feb. 21, 2014

Special Pointing (Wire) Target ● Design is complete ● Parts are here ● Assembly is underway ● Motion ○ Motion will be disabled when removed for normal target operation ○ Target motion will be disabled when pointing target is in beam. ○ Only target experts shall operate the pointing target. ● Plan to be interlocked to standard lifter in the fall 2014

Target Operator Training  A target operator required for every shift when target is cold  Joint Hall A/C target operator training All TO needs to be re-trained Target experts: Greg Smith, Silviu Covrig and J. P. Chen provide training and be on-call (24x7) New training slides (Greg Smith) 1) Training classes with slides will be provided 2) Practical in CH required 3) Set half a shift as target-on-training to get hands-on experience 4) After complete training, sign and certified by an expert  Information/communications: Hall A/C cryotarget web pages Cryotarget group web page Cryotarget operator information ing list

Cryotarget Performance  Optimize target performance, minimize density fluctuation/systematics  Two LH2 loops for the March commissioning: expect significant improvement from previous machined cells large diameter, improved flow need GMp collaboration to help with commissioning/testing  Fall: add one more loop (Silviu Covrig’s design) further improvement from calculation: average ~ 1%, maximum 4% (windows)