FMS UpdateRefurbishment for Run15

Stephen TrentalangeAugust 16, 2013

STAR Management Meeting

Status/Problems with the FMS

• Run11 New management• Run11-Run13 Physics addressed– Run 11 500 GeV AN for pions: high pT

– Run 12 200 GeV AN for pions: topology/high pT

– Run 13 500 GeV ALL for pions; glue at low x

• Problems increasing with time:– Increase in gain variations in large cells ~50->~300– Graying of lead glass due to radiation damage

Tasks/People

• Summer 2013– Remove FMS lead glass/unwrap cells (5mm)– Expose to sunlight (2mm)

• Fall/Winter 2013– Fix large cell PMT bases (???)– Glue PMTs to lead glass (5 mm)– Re-wrap cells with aluminized mylar (3mm)

• Summer 2014– Re-stack FMS (6mm)– Test electronics (3mm)

• People: Trentalange/Mondal/Dilks/Heppelman/Marshall/Boone + extra UCLA/PSU/StoneyBrook/Valparaiso Students, as needed

FMS Problems: PMT Gain Drift

We

Gain jumps

Gain Drifts

PMT Base Circuit DiagramLED Amplitude vs Time

10K SecondsWe can follow gain vs time with LEDs, but trigger becomes extremely unreliable.

Radiation Damage to Lead Glass

• Damage inversely proportional to distance from beamline• Radiation hardened lead glass positioned closest to beamline• Problem much less for large cells

Run 12 Run 13

Day Day

LED pulseamplitude

PMT Health

No SignalGain JumpsGain VariesMultiple

Small cells :Radiation damageLarge cells : Gain problems~41% (323) bases

Radiation Damage/Exposure to Sunlight

0 hours 15 hours 40 hours

300 500 700 900 Wavelength (nm)

300 500 700 900 Wavelength (nm)

Rela

tive

Abso

rptio

n

Rela

tive

Abso

rptio

n

Large Cell Small Cell

Repair of PMT bases

Bases potted in insoluable* rubber/ repair time is ~1+ hour/base + ~10-20 componentsRisk mechanical damage to tubes, base components. Other 60% of tubes NOT repaired might fail in similar fashion. * Checked alcohols, acetone, dimethyl chloride, gasoline, oils, acetic acid, heat

PMT Repair: Suggest new PMTs

(Elke Aschenauer’’s contacts at Fermilab)– CDF Decommisioning Manager Jonathan Lewis

offers 750 EMI 9954 (51mm) PMTs– 100 EMC 9814 (51 mm) available– Suggests D0/INFN may have more– Additional request to George Ginther, D0

Decommisioning Manager– Additional ~900 Hamamatsu R580 (34 mm) These

might be useful for the preshower detector.

PMT Replacement

• Each tube/base needs testing• Glue/optical coupling?• HV/signal connectors and cables? Current FMS

uses “bayonet”-style HV connector. May need to find/buy 788 SHV bulkheads for patch panel, plus 788 lemo cables/lemo-bnc adapters

• Additional problems?

Conclusions

• FMS Disassembly: finished• Exposure to sunlight: in progress– 100% for small cells– 12% of large cells

• Repair of PMTs too difficult; exploring promising sources for new PMTs

• Budget depends on connectors/style of new PMTs. ROUGHLY ~$20-40K?