General Meeting Summary 7/19/17

DETECTORS AT JLAB (Arthur, Vardan)

SHMS AEROGEL CERENKOV DETECTOR

• Recent cosmic run confirms light yield of n=1.011 aerogel is 7 photoelectrons

• Discussion about observed background of ~2 photoelectrons

• Largely consistent with what one may expect from noise from PMT based on studies with HMS aerogel detector
• Discussion of other possible sources: scintillation (correlated with actual event), reflections in diffusion box from previous tracks

• scintillation is most likely as shown in cosm2

• Real question is the impact of this background on experiments

• For HMS detector cut at 1 p.e. for total of 8 p.e. (SP15) in 2003 - no impact on physics
• However, HMS aerogel degraded over time and had to cut higher in 2007 - starting to impact physics

• Discussion about ADC channel 6 - drops out and goes negative

• Note that plot shown is pedestal subtracted, so if noise contribution then negative is not a surprise
• Investigate impact of power supply, cabling, bases/divider, connectors, etc

• Action Items:

• estimate rejection factors for PID with and without background
• Figure out why ADC channels seem to drop out
• Plan on exchanging aerogel tray from SP-11 to SP-30 (tentatively August)
• When beam available and there is an opportunity to install SP-11 again, check for events below threshold

HMS AEROGEL CHERENKOV DETECTOR (Salim)

• In process of removing all PMTs from aluminum cylinders

• Investigating composition of PMT glass windows - helium permeability

• In process of selecting 16 good PMTs from the list of Photonis XP4500

• 1 good one at CUA
• installed in detector that was at CERN are XP4572

• Note on JLab Hall C helium level

• HMS quadrupole has helium leak that is being fixed
• Measurements of helium level of SHMS detector hut (where our new SHMS aerogel detector is installed!) planned in next few weeks
• Hall considers to install a system that warns of elevated helium levels and another to flush detectors

PION AND KAON STRUCTURE FUNCTIONS (Dannie, Andres)

• installed a virtual machine and configured ROOT on linux environment, and able to run the code

• going through the code and making sure that understanding and doing things correctly and efficiently

• some inconsistencies in the way that error bars were being computed in a

function are being addressed

• initial plots from the simulation available

• preparing to install detector simulation GEMC for resolution studies

REFLECTOR STUDIES (Casey)

• Developing a method to quantify impact of reflectors on crystal performance

• Tested different materials, different layers and planning measurements with combinations of reflectors

• initial results available - more layers improve the light yield for teflon (a reflective material, so more layers help)
• need to better understand what the materials are (mylar, tedlar?)
• Test additional known materials: Gore reflector (as in aerogel), specular reflector

• Action Items:

• Measure thickness of materials
• test if one side of mystery materials scratches, the other doesn't - if so, then it's aluminized mylar
• Check how many ADC channels the pedestal double peaks are apart and how this number compares to the total number of ADC channels

• note that is look for single photoelectron measurements this may not be sufficient even if small

• Exchange ADCS: take PMT spectrum with current ADC for reference, change ADC with no other changes in system, take another PMT spectrum and compare

CRYSTAL DRAWING PROTOTYPE (Blessed, Richard)

• Discussion of Blessed's presentation

NEXT MEETING: WED 26 JULY at 10:00 AM (EDT)