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AXAS (Analog X-ray Acquisition System) |
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Silicon-Drift-Diode System with complete analog electronics
The new Analog X-ray Acquisition System (AXAS) is a state of the art silicon radiation detector system including KETEKs SDD, preamplifier, shaper, internal power supplies and an active temperature control.With all this integrated into a solid metal housing (230 x 78 x 39 mm3) a compact system is available that gives a preamplified, shaped output signal and needs ± 12 V (approx. 4 W) as input only.
Connecting AXAS to either an AXAS MCA or a FAST ComTec MCA-3 multichannel Analyzer and a AXAS-PS power supply an easily transportable measurement setup
is achieved that can be fully operated using a laptop or notebook computer.
AXAS can be delivered with a high vacuum adapter (for operation in vacuum as low as 10-8 mbar) and a maximum detector finger length of 300 mm (100 mm standard).
The combination of the unique properties of the Silicon Drift Detector and our reliable electronics (including a pile-up rejector) lead to an excellent energy resolution even at high-count rates.
Depending on the type of detector you choose an AXAS offers different advantages.
The V-type AXAS shows an excellent peak position stability and a change of the energy resolution of only a few eV up to the maximum output countrate of about 50 kcps (input count rate 100 kcps). Whereas the P-type AXAS still offers the best possible resolution values down to 133 eV and better in the range between 1 and 103 cps and can handle input count rates up to 106 cps (350 kcps output count rate).
The AXAS system is shown here mounted to an AXAS MCA which is available as a 2k and 4k version (see separate datasheet). The versatile MCDWIN operating software
enables the user to completely control the AXAS MCA from any MS-Windows compatible computer and displays the acquired spectrum. A DLL is optionally offered for labVIEW, C and Visual Basic.
| Selection Chart | |||
| Model | Description | Peak to Backgr. | Order No. |
| AVH7-ZR1BE-139 | Si drift detector with temp controller, preamp, - 7 mm², <= 139 eV | >3000 | AV070 |
| AVH7-ZR1BE-144 | Si drift detector with temp controller, preamp, - 7 mm², <= 144 eV | >3000 | AV071 |
| AVH7-ZR1BE-149 | Si drift detector with temp controller, preamp, - 7 mm², <= 149 eV | >3000 | AV072 |
| AVH7-ZR1BE-155 | Si drift detector with temp controller, preamp, - 7 mm², <= 155 eV | >3000 | AV073 |
| AVH7-MO1BE-144 | Si drift detector with temp controller, preamp, - 7 mm², <= 144 eV | >3000 | AV074 |
| AVH7-MO1BE-149 | Si drift detector with temp controller, preamp, - 7 mm², <= 149 eV | >3000 | AV075 |
| AVH7-MO1BE-155 | Si drift detector with temp controller, preamp, - 7 mm², <= 155 eV | >3000 | AV076 |
| AVH7-PD1BE-144 | Si drift detector with temp controller, preamp, - 7 mm², <= 144 eV | >3000 | AV077 |
| AVH7-PD1BE-149 | Si drift detector with temp controller, preamp, - 7 mm², <= 149 eV | >3000 | AV078 |
| AVH7-PD1BE-155 | Si drift detector with temp controller, preamp, - 7 mm², <= 155 eV | >3000 | AV079 |
| AVH10-ZR1BE-139 | Si drift detector with temp controller, preamp, - 10 mm², <= 139 eV | >400 | AV101 |
| AVH10-ZR1BE-144 | Si drift detector with temp controller, preamp, - 10 mm², <= 144 eV | >400 | AV102 |
| AVH10-ZR1BE-149 | Si drift detector with temp controller, preamp, - 10 mm², <= 149 | >400 | AV103 |
| AVH10-ZR1BE-155 | Si drift detector with temp controller, preamp, - 10 mm², <= 155 eV | >400 | AV104 |
| AVH80-ZR5BE-180 | Si drift detector with temp controller, preamp, - 80 mm², <= 180 eV | >3000 | AV801 |
| AVH80-ZR5BE-200 | Si drift detector with temp controller, preamp, - 80 mm², <= 200 eV | >3000 | AV802 |
| AVH80-ZR5BE-240 | Si drift detector with temp controller, preamp, - 80 mm², <= 240 eV | >3000 | AV803 |
| AVH100-ZR5BE-180 | Si drift detector with temp controller, preamp, - 100 mm², <= 180 eV | >400 | AV1001 |
| AVH100-ZR5BE-200 | Si drift detector with temp controller, preamp, - 100 mm², <= 200 eV | >400 | AV1002 |
| AVH100-ZR5BE-240 | Si drift detector with temp controller, preamp, - 100 mm², <= 180 24 | >400 | AV1003 |
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| AXAS Options | |||
| Model | Description | Order No. | |
| ASH015 | Gaussian shaper, 0,15 μs shaping time | ASH015 | |
| ASH025 | Gaussian shaper, 0,25 μs shaping time | ASH025 | |
| ASH050 | Gaussian shaper, 0,50 μs shaping time | ASH050 | |
| ASH100 | Gaussian shaper, 1 μs shaping time | ASH100 | |
| ASH200 | Gaussian shaper, 2 μs shaping time | ASH200 | |
| ASH300 | Gaussian shaper, 3 μs shaping time | ASH300 | |
| AVAC | Vacuum tight model | AXOYAC | |
| AFL160 | extended detector finger: 160 mm length (aluminium) | AXO100 | |
| AFL300 | extended detector finger: 300 mm length (aluminium) | AXO300 | |
| AFL200 | extended detector finger: 200 mm length (V2A) | AXO200 | |
| -PD (7mm2 only) | detector module with Pd collimator | AXOPD | |
| APS115 | external power supply (input: 110Va.c.; output: + / - 12 V) | AXPS110 | |
| APS230 | external power supply (input: 230Va.c.; output: + / - 12 V) | AXPS230 | |
| -LE (P only) | low energy module with polymer window (incl. -VAC) (not for V models) | AXOLE | |
| AETR | electron trap | AXOET | |
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AVH means AXAS VITUS SDD with external FET (eFET-SDD)
The energy resolution is measured in terms of Full Width at Half Maximum (FWHM) of the 55Fe Mn Kα line, with 1 kcps, optimum shaping time (1μs typical), and an energy range of 1 to 20 keV. The spectroscopic results are guaranteed for an AXAS housing temperature of +20°C.
The peak to background ratio is the relation of the peak value of 55Fe Mn Kα (5.9 keV) and the mean floor value between 800 eV and 1200 eV, measured at -20°C, 1 kcps, optimum shaping time (1μs typical) and 1 cm distance between SDD and source.
The energy range for all detector models is 1-20 keV, the upper energy limit is changeable on customers demand. Values up to 30 keV are possible.
The radiation hardness is guaranteed up to a total dose of 1012 absorbed photons on the SDD active area. The typical variation of the energy resolution in terms of FWHM is less than 2% after this dose. The P/B ratio variation is less than 10%
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Scientific Concept of the Silicon Drift Detector
The basic form of the Silicon Drift Detector (SDD) was proposed in 1983 by Gatti and Rehak. Intensive further
development by Josef Kemmer and others improved this concept and led to a commercially available product in 1998, manufactured by his company KETEK for FAST ComTec.
The detector consists of a volume of fully depleted silicon in which a strong component parallel to the surface of the electric field “drifts” signal electrons towards a small sized collecting anode. As shown in the schematic drawing below, one side of the detector is covered by a number of increasingly reverse biased field rings generating the drift field. The radiation entrance side is the non structured p+-junction denoted in the figure as back contact, giving a homogeneous ensitivity over the whole detector area. As the device is fully depleted the total thickness of 0.45 mm is sensitive to the absorption of X-rays
VITUS Model with external FET
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The outstanding property for the SDDs is the extremely small value of the anode capacitance which is practically independent of the active detector area. This feature allows to gain a higher energy resolution at shorter shaping times (0.15 to 3 ìs) compared to conventional photodiodes and Si(Li) detectors, recommending the SDD for high count rate applications (up to 106 s-1).
The SDD shown in the graph above features an external first FET, one could theoretically integrate this first transistor on the detector chip to take advantage of the small detector output capacitance. The separation of detector and transistor, however, leads to an excellent peak stability and an almost negligible change of the resolution with increasing count rate due to the pulsed reset read-out this type features. Due to the elaborated process technology used in the SDD fabrication the leakage current of the detector is very low.
This permits an operation of the detector using a peltier cooler only. In combination with the small anode capacitance and low noise electronics energy resolutions better than 144 eV for the V-type (@ 5.9 keV) are standard.
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left: The VITUS SDD also shows only a slight peak position change due to an increasing count rate. Values less than 8 eV as shown in the graph are typical.
right: Quantum efficiency for a standard VITUS detector module. The qe of the detector itself has been as well taken into account as the absorption by the 8 um Beryllium entrance window, the 30 nm Aluminium on the detector crystal and the 1 mm of 1 bar N2 between window and detector.
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