Evaluation of novel x-ray detectors

By: Tyler StringerMentors: Drs. Hedin & LurioEvaluation of novel x-ray detectorsScintillation light when a particle/radiation strikes certain materials, which then emit lightCrystals, glass, plastics, liquids, gasesDimple = 3mm deep concave cut

MPPC, Scintillator, SiPM

SiPM = Silicon photomultiplier ... AKA MPPC (Multi-pixel photon counter)APD pixels in Geiger modeEach pixel pulses signal from detecting one photonSum of APD outputs = signal output to moduleAble to count single photons (weak light)Can operate at room temperature100 pixels, pixel size = 100 square microns, responds to 320-900nm wavelength range (peak sensitivity at 440nm)Photon detection efficiency (440nm, 0.5pe) = 45-65%Dark count (0.5pe) = 1 million counts/s = 100mV/pe (analog)Time resolution = 200-300psGate time range: 1ms-100ms (7 different intervals)Threshold level: 0.5pe-7.5pe (9 different intervals)SiPM SpecsFrequency Output: threshold half of 1pe pulse (above this = count)Analog Output: 100mV=1pe

SiPM Compared to Calibration Diode (Output vs. Detected)Advantages of SiPM over PMT:Smaller/lighterSensitivity: single photon count30-50 times less voltageImmune to magnetic fieldsLower costHowever...Large dark noise at room temperatureLarge crosstalkAfterpulsing

SiPM with scintillator tested with particles at FermilabX-rays?

30 mm1 mmPMTSiPME.g. (100,000 counts/100ms) = (1,000,000 counts/s)Increased threshold = decreased noiseProblem: (dark with no source) = (dark with source)