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This study involves irradiating single crystal diamond sensors to evaluate their performance in particle detection. Comparison with poly and single crystal sensors, re-measurements, and upcoming irradiation plans are discussed in detail. Results, challenges, and future prospects are highlighted.
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Irradiation Study of Single Crystal Diamond Sensors for the PLT • Irradiation of sensors at the PS 1.5 years ago • Comparison to RD42 irradiated poly and single • Re-measured (for a much longer time) improved CD • Upcoming irradiation plan R. Stone--Rutgers RD42 meeting 6-Mar-2009
Proton Irradiation Jul-07 • Irradiated with 24 GeV protons at CERN PS • Contacts were removed prior to irradiation for more rapid cool down • 2 diamonds tested for each fluence listed: • For the lifetime of LHC expect: 2.5 x 1015 p/cm2 (P. Bhat) • Above results are more pessimistic than those from RD42 • Note: the dark current after irradiation is < 10pA
Single Crystal Diamond Before and After 1.5 X 1015 p/cm2 Irradiation Before irradiation After Irradiation Pixel thresh Events Signal ( e- ) Signal ( e- ) Pedestal events
CVD Diamond CD vs Proton Fluence RD42 Poly Relative CD RD42 Single PLT old data Fluence (x1015p/cm2)
Test of Irradiated Diamond With Fast Electronics • Used BCM_1F frontend electronics (25 ns) instead of standard characterization stand electronics (200 ns) to check if charge collection is slower due to irradiation • Re-tested one of the diamonds that received 1.5 x 1015p/cm2 • After calibration, measured collected charge to be <10% lower than slower electronics measurements, but within calibration error and other systematic effects • Also looked at width of signal pulse: • If some charge is collected later than 25 ns, pulse will be wider than unirradiated diamond or calibration signal • No widening was observed on scope pulse (within ~5%)
Re-measurement of Irradiated Samples • One benefit of Fast Amp measurement was a hint at more charge • appearing during a much longer measurement period. • Can see many rapid jump increases in signal (next plot) • Have look so far at 2 out of the 4 irradiated diamonds • Expect to see the same effect in the other 2 (starting this month)
CD vs Time for Irradiated (1.5 x1015p/cm2) Sample CD 500 V | 600V | 1KV | 500V Time (minutes)
CVD Diamond CD vs Proton Fluence RD42 Poly Relative CD RD42 Single PLT old data PLT new data Fluence (x1015p/cm2)
Next • Re-measure other 2 irradiated diamonds, however: • They are currently being repolished to remove surface junk • Send off our 2 re-measured samples for surface cleaning and measure again. • Try using our stronger source for faster (<< 1 week) ‘pumping’ • New Irradiation at the PS this summer (Aug-Sep): • 8 new samples + 3 pixel planes (bumpbonded ROC+diamond): • Fluences (x1015p/cm2) : 4@ 0.5, 2@ 1.0, 4@ 2.0, 2@ 4.0