Diamond radiation detectors have been used in Nuclear Weapons Effects simulation at Sandia National Laboratory.[4,7] Time resolved measurements of the soft x-ray fluence from plasma radiation sources on Saturn were obtained using calibrated DRDs. These measurements show that the sensitivity of the DRDs is independent of the energy of the photons over a wide range of photon energies ranging from ≈100 eV through ≈5 keV.

 

DRDs have also been used to measure the intensity of x-rays emitted by synchrotrons.[3] These measurements consisted of both time integrated and time resolved measurements of the xray intensity. The time integrated measurements provide a monitor of the x-ray intensity as if it were emitted from a continuous source. The time resolved measurements have resolved the individual bursts of photons emitted with an x-ray pulse full width at half maximum ≈350 ps.

 

Diamond radiation detectors have also been successfully used to detect charged particles and energetic neutrons.[8] Both time resolved and time integrated (pulse counting) measurements have been made.

 

Diamond radiation detectors have the distinct advantage of being rugged and radiation hardened and require only a low DC forward bias voltage. Extremely simple circuitry is required to measure the signal generated in the diamond due to the radiation incident on it.
 

Recently Alameda Applied Sciences Corporation, in collaboration with Atomic Energy Canada Limited (AECL), has used diamond radiation detectors to measure the dose delivered by a 12 MeV electron accelerator at AECL. This accelerator is used at AECL for medical instrument sterilization. The electron beam is scanned to generate a beam size of 18 cm x 3 cm at 50% beam intensity (i.e. full width at half maximum). The dose/pulse was 0.5 kGy with a duration of 200 µs.
 

The diamond detector was biased positively and negatively with a dc voltage of 45 V. The peak signal produced by the detector (measured across a 50 Ω load) was identical for both bias polarities. Signal strength from the detector was linearly proportional to the accelerator beam current as shown in Figure 2. The beam current is proportional to the beam intensity showing that the diamond detector signal is linearly proportional to the beam intensity.
 

The dose rate at 95 mA beam current was 2.5 MGy/s. The measured signal of 850 mV across 50 Ω corresponds to 0.017 A. Therefore the sensitivity is 6.8 nA/Gy/s. A 100 Gy/s dose rate would then produce 0.68 µA. The dark current in these detectors at bias voltages ≈100 V is less than 0.1 nA, allowing an accurate measure of a dose rate as low as 100 Gy/s while also accurately measuring 2.5 MGy/s. The dynamic range of these detectors is thus very high. The question that remains is the stability of this response over time and with accumulated dose. It is these questions that the proposed research will answer.

The detector signal was Gaussian as shown in Figure 3 as the beam is scanned. The width of the signal indicates the size of the beam at the detector. Figure 3 shows the beam current (200 µs wide pulse) and the diamond response with a negative bias. The scan voltage was 75 V corresponding to a scan length of 18 cm. When the scanning length was increased from 18 cm to 60 cm the diamond signal full width at half maximum decreased inversely to 9.5 µs (shown in Figure 4).