PMT Testing at JMU -Automation and Afterpulsing

Tara JobinWilliam KemmererEric MoellerWilliam Shaver

11/11/2016

Dr. Ioana NiculescuDr. Gabriel Niculescu

James Madison University

Eric Moeller, SESAPS 2016

FU-84 PMTs

Outline

11/09/2016 Eric Moeller, SESAPS 2016

● Motivation● Our Setup● Automation● Progress● Afterpulsing● Future Plans

Motivation

● JLab Hall A○ ECAL

● 8,000 PMTs to test

Our Setup

● Custom-built● Light-Tight

Our Setup

11/09/2016 Eric Moeller, SESAPS 2016

Reflecting surface

Light

LED

● PMTs held vertically● LED in the middle and

spread by mirror● Includes a 2-inch

weakness PMT● Takes up much less

space

Our Setup

11/09/2016 Eric Moeller, SESAPS 2016

● Slow to set up● Many different

computer commands

● Many chances to make mistakes

● Data analysis by hand

● Required excessive time and attention

● Time to automate!

Screenshot of the desktop mess

Automation

11/09/2016 Eric Moeller, SESAPS 2016

● Only ONE command!● Combination of C and Python● Opens three terminals

○ HV Controller (CAEN 5527)○ Raspberry Pi○ Data Acquisition (CODA)

Automation

11/09/2016 Eric Moeller, SESAPS 2016

● Combination of ○ Shell scripts○ Expect○ C++

● Automatic pedestal runs● Runs through multiple

voltages● Automatic ROOT analysis● We use a VME-based DAQ● Produces Summary Graphs

Automation

11/09/2016

● More efficient● More accurate● More time for

homework

Afterpulsing● What is afterpulsing?● Why is afterpulsing

important?

● JLab signals at 5-10 kHz

● Occurs at the first dynode

● Ionizes gas within the tube

11/09/2016

Afterpulsing

● We shift the gate on our DAQ window○ Quad gate

● Testing with blue LED ● No amplification● PMT baking

○ No significant difference!

● Still test 1100V-1500V● Yes, we even

automated this!

Summary

11/09/2016 Eric Moeller, SESAPS 2016

Picture of PMT pallets

Picture of aluminum setup

● Hall A ECAL● Setup● Automation● Afterpulsing

Thank You!

11/09/2016 Eric Moeller, SESAPS 2016

● JMU Physics and Astronomy Department

● NSF

10/27/2016

ECAL Specs• Function: Detect 4-5 GeV Electrons• Energy resolution: σ/E 10% or better for 3.5 GeV• Spatial resolution: 6-8 mm (2 mm if using

upstream coord. Detector – GEMs)• Full Luminosity: 26-29 degrees, 8 x 1038 Hz/cm2

• Trigger: Overlapping segments correlated w/ the proton. Trigger at threshold > 75% of elastic peak

• 1500-2000+ Lead-glass blocks, readout by FEU84 photomultiplier tubes

• Need to test (@JMU) : Gain vs HV, Relative Q.E., AfterPulsing, heat damage

Our Setup

11/09/2016 Eric Moeller, SESAPS 2016

• Wooden PMT holder.• Light source “far away”.• Use geometric optics to predict

LL.• No +ve PMT placement.• Setup too long for our dark box.

• Foam PMT holder.• Circular PMT placement.• Light source “farish away”.• Use geometric optics to predict LL.• Still no +ve PMT placement.

• 3D printed PMT holder.• Circular PMT placement.• +ve PMT placement (stop)• PMTs sag if not supported at the back.

Template

11/09/2016 Eric Moeller, SESAPS 2016