PX2T-CdTe Power Supply with Analog Pulse Shaping (Discontinued)

The PX2T-CdTe has been discontinued and replaced by the PX5.

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 MCA8000D.

Figure 1. XR-100T-CdTe Connection Diagram

Figure 2. PX2T Amplifier Output

PX2T Power Supply & Shaping Amplifier Specifications

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
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

PX2T Connectors

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 &lt 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)

Rise Time Discrimination

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 PX5 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.