Monitoring Detectors

1. Special Features

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CXS-Sz20-TK: Dosis of x-rays


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CXM-GC01: Dosis of x-rays


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CXM-GC03N


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CXM-S200: Intensity of x-rays

  • output voltage is a linear function of dose rate
  • high ß-, y- and x -ray sensitivity together with a wide dynamic range
  • high stability and radiation hardness
  • small size and rugged design
  • amplifier electronics is integrated in detector package
  • no high supply voltage needed
  • insensitive against magnetic fields
  • customer designed modification and special sensor-heads
  • energy range:
    • y- and x-rays: 5 keV - 2 MeV
    • ß-rays: 25 keV - 5 MeV
  • options for system adaption:
    • sensitivity range tuning
    • spectral selection of scintillation crystals

2. Intended use

The ß-, y- and x-ray detectors of our series CXM (Crystal x-ray monitor) has a great variety of applications in x-ray technology and the ß- and y-ray detection. Examples are the stochastic and continuous y-ray control, direct and indirect dose rate measurements, absorption measurements technology.

The detector types cover the whole energy range from 5 keV to about 2 MeV, but the detection of higher energies above 2 MeV is also possible. The design of construction offers the feasibility making linear-detectors of any length. Thus positioning-resolving measurements can be performed by computer aided analysis, as, for example, in signal processing systems.

The wide energy range of the detectors allows measurements of high energy y- and x-rays.


3. Design & Function

The ß-, y- and x-ray detector CXM consists of a scintillation crystal, readout by a Si-pin-photodiode and is mounted together with a preamplifier in an Al-package. A miniaturised switch for tuning the amplification can be fixed inside the detector packaging.

The length of scintillation crystal can be adapted to the detectable energy range. For ß- and soft x- and y-radiation (5 keV < E < 30 keV) we use the direct absorption in the Si-photodiode.

The entrance window is a new developed Be-free “low energy window”. Active areas between 2…200 mm2 are available. As option the preamplifier sensitivity and characteristics can be matched to the specific application. The detectors are available with screened four-wire cable or with miniaturised connector.


4. Examples

4.1. CXM-GC01 (CXM-S80)

For dose rate measurements of x-rays.

Detector description generally monitor detector
specific for low-energy gamma and x-ray radiation
Radiation type   gamma and x-ray
Energy range keV 15...60 
Sensor   pin-Photodiode
Sensor size mm² 80
Radiation entrance window material, thickness Alu, 0,3 mm
Cases type 1
front radiation entrance
Size LxWxH  [mm³] 70x18x10
housing extension no
Connector   5-wire cable or miniaturized plug
Amplification tuning   no
Typical application   dose rate measurement - x-ray


4.2. CXM-S200

For intensity measurements of x-rays.

Detector description generally monitor detector
specific for low-energy gamma and x-ray radiation
Radiation type   gamma and x-ray
Energy range keV 15..60
Sensor   pin-Photodiode
Sensor size mm² 200
Radiation entrance window material, thickness Ti-Foil, 25µm
Cases type 8
side radiation entrance
Size LxWxH  [mm³] 90x16x10
housing extension 40x16x4
Connector   5-wire cable or miniaturized plug
Amplification tuning   no
Typical application   intensity measurement - x-ray


4.3. CXM-S80/ß

For monitoring of beta radiation sources.

Detector description generally monitor detector
specific beta-detector
Radiation type   beta radiation
Energy range keV 100 ....2500
Sensor   pin-Photodiode
Sensor size mm² 80
Radiation entrance window material, thickness Kapton; 8µm, 0,5µm AL
Cases type 6
side radiation entrance
Size LxWxH  [mm³] 90x16x10
housing extension 28x16x3
Connector   5-wire cable or miniaturized plug
Amplification tuning   no
Typical application   monitoring: beta-source


4.4. CXM-S80-U

For monitoring of PET-sources.

Detector description generally monitor detector
specific for high-energy gamma and x-ray radiation
Radiation type   gamma radiation
Energy range keV 80 ....1500
Sensor   pin-photodiode mit scintillation crystal, 10 mm thick
Sensor size mm² 80
Radiation entrance window material, thickness Alu, 0,3 mm
Cases type 1a
front radiation entrance
Size LxWxH  [mm³] 70x18x10
housing extension no
Connector   5-wire cable or miniaturized plug
Amplification tuning   yes
Typical application   monitoring: PET-source


5. Technical Data

absorption efficiency depends on radiation energy and crystal specifications
operating voltage Ub = ± 15 V, Ub min = ± 4,5 V, Ub max = ± 18 V
power consumption P < 20 mW
max. output voltage Ua max ca. 13 V (RL >= 5 kOhm)
max. output current Ia max = 15 mA
offset compensation internal adjustment, default a few mV
operating temperature -20 °C ... +45 °C
cable connector 4-wire, shielded cable
green: Ua
red: Ub = + 15 V
blue: Ub = - 15 V
yellow: grounding
shielding: housing

Attention: With high sensitivity of the sensor (transimpedance 1010 and more) and at temperatures exceeding 35° C, the sensor may require a temperature stabilization!


6. Technical Specifications

6.1. Sensors without scintillation crystal (CXM-S...)

active areas round 2, 5, 10, 50 mm2
stripes 20, 40 mm2
square 80, 200, 400 mm2
housings front entrance active areas: 2, 5, 10, 50, 80 mm2
(variant 1) 1, 2; 20, 40 mm2 (variant 4)
side entrance
(with housing extension)
active areas: 50, 80 mm2 (variant 5) 6; 200 mm2 (variant 7, 8)
electronic preamplifier (standard transimpedance 108) up to 5x1010 for higher sensitivities
optional: 3 adjustable sensitivity ranges per miniaturized switch
connector cable grey, 4-wire, shielded, Ø = 3,1 mm
cable outlet grey cables or miniaturized plugs


6.2. Sensors with scintillation crystal (CXM-Sz...)

scintillator shape / -size cylinder d = 4 ... 9 mm, l = 1 ... 40 mm
cube areas: 8x10 mm2, 10x20 mm2
length: 1 ... 20 mm
active areas round 2, 5, 10, 50 mm2
square 80, 200 mm2
housings front entrance active areas: 2, 5, 10, 50, 80 mm2
(variant 1, 2, 3)
side entrance
(with housing extension)

active areas: 50, 80, 200 mm2 (variante 5, 6, 7, 8)

electronic preamplifier (standard transimpedance 108) up to 5x1010 for higher sensitivities
optional: 3 adjustable sensitivity ranges per miniaturized switch
connector cable grey, 4-wire, shielded, Ø = 3,1 mm
cable outlet grey cable or miniaturized plug, cables with wires


7. Dose Rate Measurement

Monitor detectors of the series CXM show a strictly linear dependence between the measured output voltage and the detected dose rate. For four typical cases:

  • low radiation energy, small dose rate (Fig. 1)*
  • low level of radiation energy, high dose rate(Fig. 2)*
  • higher radiation energy, small dose rate (Fig. 3)*
  • higher radiation energy, high dose rate (Fig. 4)*

the curves are shown in the pictures. The linear dependence is clearly verified.


7.1. Low Radiation Energy (8 keV)

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Fig. 1
linearity of the output voltage
low radiation energy
small dose rate
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Fig. 2
linearity of the output voltage
low radiation energy
high dose rate

CXM-S80 (active area 80mm2 ; no scintillation crystal). Conditions: X-ray source: FF Cu4; Cu-kα with kβ-Filter (measurements made with an internally calibrated dose rate meter)


7.2. High Radiation Energy (160 keV)

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Fig. 3
linearity of the output voltage
high energy
small dose rate
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Fig. 4
linearity of the output voltage
high energy
high dose rate

CXM-SZ50 (50 mm2, with scintillation crystal 40 mm). Conditions: X-ray source – MCD 160 (Fa. rtw); (measurements made with an internally calibrated dose rate meter)


7.3. Linearity comparison: CXM-Detector -- Geiger-Müller (GM) Counter

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Fig. 5
output voltage vs. activity

The extremely high dynamic range of the CXM-detectors of up to 105 is of advantage as also shown in comparison with alternative detector principles. Especially at higher activities, the CXM-detectors remain linear over a very large activity area, while Geiger-Müller counter tubes are already saturated and work highly non-linear. Fig. 5 shows a comparison of the CXM-detector and a Geiger-Müller counter tube under identical measurement conditions.**

All CXM-Sz… and CXD-Sz... – detectors are excellently qualified for the use with PET-synthesis modules.

(detector CXM-SZ80, 10 mm CsJ:Tl-scintillation crystal, 11C-source; EGamma= 511 keV (PET))




*- Measurements with x-ray source MCD 160; Fa. rtw, Dr. Warrikhoff KG, Neuenhagen

**- Measurements at the Max-Planck-Institut Köln