Update on FMS RepairSTAR Management Meeting: Oct 10 2013

Stephen Trentalange

Completed/Planned

• Dismounted FMS• Exposed all cells to 40+ hours of sunlight• Small cells to be glued/wrapped in mylar– Russian collaborators in November/December– Mylar/glue ordered– Separate sub-task

Problems with Large Cells (~315 to be repaired)

Map of problems with large cells. White indicates no problems. Blue indicates gain jumps in discrete steps (zener diode problem), Green indicates that the gain drifts smoothly (capacitor problem?), Orange indicates both jump/drift problems present and Red means no signal detected. Problem cell cells look roughly correlated with the plane of the ring, possibly induced by radiation damage to the electronic components. About 40% of the 788 PMT bases for the large cells need repair work.

Guidelines for Repair

• Cell Spacing = 58 mm. Need to keep PMT/electronics diameter < 56 mm

• Old magnetic shields define envelope of 54.5 mm (i.d.)

• Magnetic shields are glued to lead glass/fix tubes in place with phenolic holder.

• PMTs should be recessed back from front face by cookie ~10 mm. Ease of optical contact.

• We should be able to mount/dismount tubes from rear. Separates stacking/PMT repair tasks.

Steve Heppelmann’s Estimates $25-38/basehttps://drupal.star.bnl.gov/STAR/system/files/OldFMSBases.pdf

Large Cells: Option 1

• Fix ~500 bad bases (actual number ~315)• Reuse old FMS tubes• Make new circuit boards• Cut phenolic ring above old circuit board,

recover wire stubs, glue on new circuit board• Hold in place using new phenolic ring/or cutout

of old phenolic ring• Reuse old HV/signal cables/strip and solder to

new boards

Large Cells: Option 1

• Boards + Labor: $25-38• Cookies RTV 615: $8-17 • Total: $33-55

Replace 500 bases: $33-55 = $16,500-27,500

Large Cells: Option 2

• Tentative offer of 750 tubes from CDF. – No follow-thru, responses to inquiry ???– Tubes are OK, but bases need extensive working• Wrong diameter/need machining• Resistive only/~1 mA -> more severe sagging• SHV/strange signal; needs reworking to reuse FMS

HV/signal cables.• Must machine FMS magnetic shields to be shorter+ set

screws to hold PMTs in place.

Large Cells: Option 2 (CDF)

• Boards: $15-28• Sockets: $60• Cookies RTV 615 : $8-$17• Total: $83-105

Replace 500 bases: $83-105 = $41,500-52,500

Additional Needs

• Money– Need startup funds ~$1000’s. Order epoxy/mylar ($450/$400)– Option 1 (OLD PMTs):$16,500-27,500– Option 2 (CDF PMTs):$42,500-52,500

• Laboratory Space– Currently in 912 Phenix tent + high bay space– Zhangbu’s lab in chemistry? – Clean room in Assembly Building?

• Probably OK for manpower– Russian Visitors November/December?– PSU students/incidental machining– UCLA/PSU/TAMU staff