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The PX2T-CdTe has been discontinued and replaced by the PX4.
The PX2T-CdTe Shaping Amplifier and Power Supply for the XR-100T-CdTe is AC powered. It includes a spectroscopy grade shaping amplifier with a fixed shaping time constant (3 µs) and all the necessary power supplies for the XR-100T-CdTe. The output of the PX2T-CdTe must then go to an external MCA such as the MCA8000A.
Figure 1. XR-100T-CdTe Connection Diagram
Figure 2. PX2T Amplifier Output
General | |
| Size | 6 x 6 x 3.5 inches (15.3 x 15.3 x 8.9 cm) |
| Weight | 2.5 lbs (1.15 kg) |
Shaping amplifer | |
| Polarity | Positive unipolar |
| Shaping Time | 3 µs |
| Pulse width | 7.2 µs FWHM, see Figure 2 |
| Shaping type | 7 pole "Triangular" with Base Line Restoration, Pileup Rejection, and Rise Time Discrimination (RTD) |
| Sensitivity with XR-100T-CdTe | 6 to 60 mV/keV |
| Output range | +6.0 volts into 500 ohm load |
| Output impedance | 50 ohms |
| Input from XR-100T-CdTe | Front panel BNC |
| Output to MCA | Front panel BNC |
| Pileup Rejection (PU) | Rear panel BNC, Positive TTL For the duration of this output gate, any detected pulse must be rejected by the MCA. |
| Input Count Rate (ICR) | Rear panel BNC, Positive TTL < 2µs When connected to a counter, the ICR countrate corresponds to the total number of x ray events that strike the detector. |
| Probe power | 9-pin D-connector (cable provided) Pin 1: +8 volt preamp power Pin 2: -8 volt preamp power Pin 3: 0 to +4 V @ 350 mA cooler power Pin 4: +8 volt temperature monitor power Pin 5: +H.V. detector bias, +500 volt max. Pin 6: Ground and case Pin 7: Cooler power return Pin 8: Ground and case Pin 9: Ground and case |
| AC power | Standard IEC 320 receptacle, 110-250 VAC, 50/60 Hz (cable provided) |
Electron/hole pairs created by radiation, which interact with the CdTe near the back contact of the detector, result in fluctuations of charge collection times. These fluctuations are observed as rise time variations of the voltage step at the output of the charge sensitive preamplifier. As a result, the acquired spectra suffer from increased background counts and degraded energy resolution. To reduce these effects, a Rise Time Discrimination (RTD) circuit has been developed for the PX2T amplifier. When the RTD is active, the shaped pulses are internally gated and only pulses corresponding to "full charge collection" events are allowed to be sent to the Multichannel Analyzer (MCA) for analysis.
Because the PX2 does not have a variable high voltage supply (limited to 500 V), RTD must be used to improve the spectrum. The PX4 has a vaariable high voltage supply. When the HV is increased, the charge collection is improved and RTD is not necessary.
Figure 3. 57Co Spectrum with RTD on and off.
Figure 4. XR100T-CdTe/PX2T-CdTe/MCA8000A Connection Diagram.
Revised Januray 13, 2009