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A muon Veto for the Ultra-Cold Neutron Asymmetry Experiment Vince Bagnulo
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tarix | 08.09.2018 | ölçüsü | 7,88 Mb. | | #67387 |
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Vince Bagnulo LANL Symposium 2006
UCNA Experiment
What are cosmic ray muons? Muons are a fundamental particle, very similar to electrons, but heavier (m = 207 me) Cosmic rays are high- energy particles, mainly protons, from the sun and extra-solar sources Cosmic rays impinge on Earth's atmosphere, causing cascade of secondary particles – including muons At ground level, cosmic ray muons have the following parameters: - E 4 GeV - angular distribution cos2() - flux 1 muon/ cm2/ min
Correcting for Muon Background
Proposed Muon Veto Goal: Intercept cosmic ray muons that will impinge on primary detectors with efficiency of at least 90% Solution: Surround primary detectors with plastic scintillator detectors:
Scintillator re-emits energy deposited by ionizing radiation in the form of visible light. Visible light photons transmitted to photomultiplier tube (PMT) through use of total internal reflection A photomultiplier tube (PMT) attached to the plastic scintillator converts the light to an electronic signal and amplifies it
Initial State (beginning of summer 2006) One prototype muon veto paddle constructed Challenges: - veto paddles constructed out of salvaged scintillator (effectiveness uncertain) - PMTs located in 30 gauss field - scintillator paddles are large and unwieldy
My Task Measure efficiency of prototype veto paddle as a function of position: - establish testing procedure - help evaluate quality of scintillator Help evaluate feasibility of plastic scintillator veto concept Build production veto paddles
Efficiency = detected muons/ incident muons Used cosmic ray muons to test efficiency Using one trigger paddle found efficiency 0% High singles rate due to gamma background:
Testing Method Add second trigger paddle and required coincidence to lower background Estimate double Compton scattering could occur to 0.1 - 1% of background gammas Two trigger paddle coincidence rate: 4.0 Hz Expected: 3.33 Hz Still not sufficient. Three trigger paddles might be necessary
Testing Results (two trigger paddles)
Conclusion Currently, performance of prototype veto paddle is not sufficient A new paddle is being constructed and will be tested If satisfactory, remaining paddles will be constructed If not, alternative methods of carrying out veto will be investigated
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