New CZT Handled spectrometer

Karim BOUDERGUI, Vladimir KONDRASOVS

CEA, LIST, Sensors & Electronic Architectures Laboratory, 91191 Gif-sur-Yvette CEDEX, FRANCE

INTRODUCTION SPECIFICATIONS

MOBISIC drone

CONCLUSION

MEASUREMENTS

Experimental results show a good linearity between measured and reference dose rates and better energy resolution due to CZT quality improvement over last years (6.7 keV at 662 keV and 9 keV at 1.17 and 1.33 MeV) and high robustness against vibrations. So, this new gamma spectrometer represents a very suitable tool in the frame of dismantling process, incidental or accidental interventions.With its small size and its communication module, this new gamma spectrometer could be used as a wireless sensor. In this context, we study network integration of hundreds of this gamma spectrometer, in term of performances and response time. A second generation of digital gamma spectrometer is currently developed by CEA List to integrate new real time processing.

The identification of radionuclide is essential in many incidental or accidental interventions to evaluate correctly biological risk. It allows the diagnostic of the contamination and the identification of its origin. Moreover, it allows the identification of the different radionuclides and the corresponding equivalent dose rates, to reduce properly workers received doses. In situation contamination measurements present additional constraints. The detector must allow the best mobility and autonomy to its user (the only additional tool should be a notebook to collect data). It must minimize contamination risks and should be available at low price. Therefore, a small gamma spectrometer easy to start and usable at room temperature is becoming a crucial asset in contamination measurements. In this context, a new CdZnTe semiconductor (CZT) detector equipped with miniature electronic has been developed at CEA LIST.

The gamma spectrometer has been integrated in a drone in the frame of the MOBISIC research System@tic project. This drone has been developed for crisis interventions (attacks in urban areas, subways, tunnels, earthquake etc…) and presents a poor load capability.

NuclearEmitter: Gamma.Detector: CdZnTe quasi-hemispherical detectorDetector Volume : <60 mm3 to 500 mm3

Energy resolution: 6.7 keV at 662 keVEnergy range: 10 keV to 3 MeV.Display: Provided by host instrument or PC.

ElectricalPower: Supplied by PC (USB) or Battery

MechanicalDimensions : 75 x 40 mm (2.9 in. x 1.57 in.) (L x D).Weight: 20 g (0.044 lb).

EnvironmentalTemperature: 0 °C to +40 °C (32 to +104 °F).

Figure 5. GAM Portable Gamma-Ray Detector prototype

A relative difference between measured and reference dose rates is bellow 6 % for 60Co source (considering the 1.17 MeV peak).

Figure 4 : Real time counting rate and filtered dose rate measured with a 60Co irradiator at 18 μSv/h.

Good identification (stability of the peak position) even for short acquisitions.

Regarding the quantification of the source activity, the uncertainty can vary up to 30%.

PE1 = 68038x - 0.0083R2 = 0.9997

PE2 = 44356x + 0.004R2 = 0.9989

0.01

0.1

1

1.00E-07 1.00E-06 1.00E-05 1.00E-04

dD/dt (Gy/h)

PE1

PE2

Linéaire (PE1)

Linéaire (PE2)

Figure 1 : Integral photoelectric peaks depending on the dose rate for 60Co

0

0.5

1

1.5

2

2.5

0 200 400 600 800 1000 1200 1400 1600

E (keV)

Co @2cm -10s (c/s)

Co @2cm -100s (c/s)

Co @2cm -1000s (c/s)

0

0.02

0.04

0.06

0.08

0.1

0.12

400 450 500 550 600 650 700 750 800

E (keV)

Am

p.

(a.

u.)

BdF (c/s)

Cs (c/s)

Fit

Linearity

Energy resolution

60Co vs acquisition time

Figure 3 : 137Cs gamma spectrum Figure 2 : 137Cs spectrum with a CZT 60 mm3

The energy resolution was evaluated to 6.7 keV at 662 keV

Figure 6 : MOBISIC drone

Figure 7 : MOBISIC drone with CZT spectrometer