The charge collection apparatus 

An aparatus has been designed at SCIPP to measure charge collection efficiency (CCE). A sensor is mounted to a daughterboard and wire bonded to a pinout connector for signal readout. The output is AC coupled to remove the DC component of the signal, therefore removing the voltage offset. The daughterboard then connects to a motherboard which houses the signal charge amplifier.  A Strontium-90 (90Sr) beta emitting source is placed normal to the sensor such that the β-particles are incident upon the sensor surface. On the opposite side of the sensor, a plastic scintillator is arranged so that emitted particles that pass through the sensor are detected. Attached to the scintillator is a photomultiplier tube (PMT) which sends the detected signal to a discriminator and pulse counter. The signal from the PMT is then used to trigger a Tektronix digital storage oscilloscope on the amplified waveform that is then digitized and stored on a storage disk for data analysis. An external network, including a CR differentiator, 32 dB attenuator, a Sonoma Instrument 310 SDI amplifier, and a RC integrator was used to further amplify the pulse and shape it.

Schematic and animation of the charge collection apparatus