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149 eV Resolution!All solid state design... No more liquid nitrogen! |
XR-100 Landed on Mars!
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The XR-100CR is a new high performance x-ray detector, preamplifier, and cooler system using a thermoelectrically cooled Si-PIN photodiode as an x-ray detector. Also mounted on the 2-stage cooler are the input FET and a novel feedback circuit. These components are kept at approximately -55 °C, and are monitored by an internal temperature sensor. The hermetic TO-8 package of the detector has a light tight, vacuum tight thin Beryllium window to enable soft x-ray detection. The XR-100CR represents a breakthrough in x-ray detector technology by providing "off-the-shelf" performance previously available only from expensive cryogenically cooled systems. |
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Features
Additional Information
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Applications
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The resolution for the the 5.9 keV peak of 55Fe is 145 eV FWHM to 260 eV FWHM depending on detector type and shaping time constant. See Selection Guide.
X-rays interact with silicon atoms to create an average of one electron/hole pair for every 3.62 eV of energy lost in the silicon. Depending on the energy of the incoming radiation, this loss is dominated by either the Photoelectric Effect or Compton scattering. The probability or efficiency of the detector to "stop" an x-ray and create electron/hole pairs increases with the thickness of the silicon. See efficiency curves.
In order to facilitate the electron/hole collection process, a 100-200 volt bias voltage is applied across the silicon depending on the detector thickness. This voltage is too high for operation at room temperature, as it will cause excessive leakage, and eventually breakdown. Since the detector in the XR-100CR is cooled, the leakage current is reduced considerably, thus permitting the high bias voltage. This higher voltage decreases the capacitance of the detector, which lowers system noise.
The thermoelectric cooler cools both the silicon detector and the input FET transistor to the charge sensitive preamplifier. Cooling the FET reduces its leakage current and increases the transconductance, both of which reduce the electronic noise of the system.
Since optical reset is not practical when the detector is a photodiode, the XR-100CR incorporates a novel feedback method for the reset to the charge sensitive preamplifier. The reset transistor, which is typically used in most other systems has been eliminated. Instead, the reset is done through the high voltage connection to the detector by injecting a precise charge pulse through the detector capacitance to the input FET. This method eliminates the noise contribution of the reset transistor and further improves the energy resolution of the system.
A temperature monitor diode chip is mounted on the cooled substrate to provide a direct reading of the temperature of the internal components, which will vary with room temperature. Below -20 °C, the performance of the XR-100CR will not change with a temperature variation of a few degrees. Hence, closed loop temperature control is not necessary when using the XR-100CR at normal room temperature. For OEM applications or hand held XRF instrumentation a closed loop temperature control is recommended. The Active Temperature Control is optional in the PX2CR and standard in the PX4.
Most of Amptek’s detectors contain internal collimators to improve spectral quality. X-rays interacting near the edges of the active volume of the detector may produce small pulses due to partial charge collection. These pulses result in artifacts in the spectrum which, for some applications, obscure the signal of interest. The internal collimator restricts X-rays to the active volume, where clean signals are produced. Depending on the type of detector, collimators can
The XR-100CR can be operated in air or in vacuum down to 10-8 Torr. There are two ways the XR-100CR can be operated in vacuum: 1) The entire XR-100CR detector and preamplifier box can be placed inside the chamber. In order to avoid overheating and dissipate the 1 Watt of power needed to operate the XR-100CR, good heat conduction to the chamber walls should be provided by using the four mounting holes. An optional Model 9DVF 9-Pin D vacuum feedthrough connector on a Conflat is available to connect the XR-100CR to the PX2CR or PX4 outside the vacuum chamber. 2) The XR-100CR can be located outside the vacuum chamber to detect X-Rays inside the chamber through a standard Conflat compression O-ring port. Optional Model EXV9 (9 inch) vacuum detector extender is available for this application. Click here for more information on vacuum applications and options.
| General | |
| Detector Type | Si-PIN |
| Detector Size | From 5 mm2 to 25 mm2, See Selection Guide |
| Silicon Thickness | 300 µm, 500 µm, 680 µm. See efficiency curves |
| Energy Resolution @ 5.9 keV (55Fe) | 145 eV FWHM to 260 eV FWHM depending on detector type and shaping time constant.
See Selection Guide |
| Background Counts | <3 x 10-3/s, 2 keV to 150 keV for 7 mm2/300 µm detector |
| Detector Be Window Thickness | 1 mil (25 µm),or 0.5 mil (12.5 µm), See transmission curves |
| Charge Sensitive Preamplifier | Amptek custom design with reset through the H.V. connection |
| Case Size | 3.75 x 1.75 x 1.13 in (9.5 x 4.4 x 2.9 cm) |
| Weight | 4.4 ounces (125 g) |
| Total Power | <1 Watt |
| Warranty Period | 1 Year |
| Typical Device Lifetime | 5 to 10 years, depending on use |
| Storage time | 10+ years in dry environment |
| Operation conditions | 0°C to +40°C |
| Inputs | |
| Preamp Power | ±8 to 9 V @ 15 mA with no more than 50 mV peak-to-peak noise |
| Detector Power | +100 to 200 V @ 1 µA (varies for different detector types) very stabe <0.1% variation |
| Cooler Power | Current = 350 mA maximum, voltage = 4 V maximum with <100 mV peak-to-peak noise Note: the XR-100CR includes its own temperature controller |
| Outputs | |
| Preamplifier Sensitivity | 1 mV/keV typical (may varry for different detectors) |
| Preamplifier Polarity | Negative signal output (1 kohm maximum load) |
| Preamplifier Feedback | Reset through the detector capacitance |
| Temperature Monitor Sensitivity | PX2CR: 770 mV = -50 °C PX4: direct reading in K through software. |
| Preamp Output | BNC coaxial connector |
| Power and Signal | 6-Pin LEMO connector (Part# ERA.1S.306.CLL) |
| Interconnect Cable | XR100CR to PX2CR: 6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 9-Pin D (5 ft length) XR100CR to PX4: 6-Pin LEMO (Part# FFA.1S.306.CLAC57) to 6-Pin LEMO (5 ft length) |
| Pin 1 | Temperature monitor diode |
| Pin 2 | +H.V. Detector Bias, +100 - 200 V maximum |
| Pin 3 | -9 V Preamp power |
| Pin 4 | +9 V Preamp power |
| Pin 5 | Cooler power return |
| Pin 6 | Cooler power 0 to +4 V @ 350 mA |
| Case | Ground and shield |
Figure 2. XR100CR Detector Extender Options.
Power to the XR-100CR is provided by either the PX4 or the PX2CR:
A) The PX4 is DC powered by an AC adaptor and provides both a variable Digital Pulse Shaping Amplifier (0.330 µs to 45 µs shaping time) and the MCA function.
B) The PX2CR is AC powered and also includes a spectroscopy grade Analog Shaping Amplifier with fixed shaping time constant (6 µs, 12 µs or 20 µs). The output of the PX2CR must then go to an external MCA such as the MCA8000A.
The XR-100CR/PX2CR or XR-100CR/PX4 systems ensures stable operation in less than one minute from power turn-on.
The PX4 Digital Pulse Processor, MCA, and Power Supply for the XR-100CR is DC powered by an AC adaptor. It provides a variable Digital Shaping Amplifier (0.330 µs to 45 µs shaping time), the MCA function, and all necessary power supplies for the XR-100CR.
Figure 3. This diagram shows the internal connections between the AXRCR hybrid sensor and the electronics within the case, as well as the external connections to the PX4.
Figure 4. Resolution vs. input count rate (ICR) for various peaking times. Taken with XR100CR and PX4.
Figure 5. Throughput for various peaking times. Taken with XR100CR and PX4.
The PX2 Shaping Amplifier and Power Supply for the XR-100CR is AC powered. It includes a spectroscopy grade shaping amplifier with a fixed shaping time constant (6 µs, 12 µs or 20 µs) and all the necessary power supplies for the XR-100CR. The output of the PX2CR must then go to an external MCA such as the MCA8000A.
Figure 6. This diagram shows the internal connections between the AXRCR hybrid sensor and the electronics within the case, as well as the external connections to the PX2CR.
Figure 7 (linear). Shows the intrinsic full energy detection efficiency
for the XR-100CR detectors. This efficiency corresponds to the probability
that an X-ray will enter the front of the detector and deposit all of its
energy inside the detector via the photoelectric effect.
Figure 8 (log). Shows the probability of a photon undergoing any
interaction, along with the probability of a photoelectric interaction
which results in total energy deposition. As shown, the photoelectric
effect is dominant at low energies but at higher energies above about 40
keV the photons undergo Compton scattering, depositing less than the full
energy in the detector.
Both figures above combine the effects of transmission through the Beryllium window (including the protective coating), and interaction in the silicon detector. The low energy portion of the curves is dominated by the thickness of the Beryllium window, while the high energy portion is dominated by the thickness of the active depth of the Si detector. Depending on the window chosen, 90% of the incident photons reach the detector at energies ranging from 2 to 3 keV. Depending on the detector chosen, 90% of the photons are detected at energies up to 9 to 12 keV.
PDF file of coefficients (29 k). This file is provided for general information. It should not be used as a basis for critical quantitative analysis.
For its unique design and reliability, this detector was selected for the Pathfinder Mission
to perform rock and soil analysis using x-ray fluorescence techniques.
Figure 9. Courtesy of the University of Chicago.
Figure 10. Complete XRF system.
New! XR-100SDD with Silicon Drift Detector (SDD)
XR-100CR Specifications in PDF (382k)
Revised April 22, 2008