Double-sided Silicon Strip Detectors
The double-sided silicon strip detector (DSSD) is ideal for
detecting charged-particle emission from nuclei at the proton drip line.
Their thin profile to betas (60-micron thickness)
and high granularity make them the detector of choice in the search for
proton and alpha spectroscopy. These detectors may be located at
the final focus of the
Recoil Mass Spectrometer (RMS)
or at the achromatic focus if mass identification is unnecessary.
The DSSD is located behind the RMS focal plane detector (PSAC). Heavy ions are implanted into a 60-micron thick DSSD with 40 horizontal and 40 vertical strips. This strip arrangement results in a total of 1600 pixels, each acting as an individual detector. For each event in the DSSD, the time (from a continuously running clock), energy, and event type (recoil or decay, depending on whether it is in coincidence with the focal plane detector) are recorded. By using this time information, the half-life of the decaying nuclide is determined. Individual strips are gain-matched in software through the use of external alpha sources and on-line produced known particle activities.
The DSSD detector system has been developed both as a stand-alone detector (for ground-state proton and alpha decay studies), and in conjunction with a thick Si (500 micron, 2500 mm2) and a 70 mm diameter X-ray detector (30-mm thick Ge) located just behind it (for the study of beta-delayed proton emission).
New electronics, based on the digitization of the preamplifier signal and analysis of the waveform, has been implemented. Based on the DGF-4C CAMAC module by X-Ray Instrumentation Associates. The advantage of these electronics is the enlarged bandwidth capability and the resulting lower energy and time thresholds. In conventional electronics, the preamplifier signal is split into high gain (decay events) and low gain (implantation) circuits. The high gain circuit is blinded by the implantation of the heavy ion for 5-10 us. By digitizing the preamplifier signal in 25 ns steps, the waveform can be analyzed and small signals (fast decay events) generated immediately (from 5 us) after implantation may be recorded.
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