Все науки. №10, 2024. Международный научный журнал - страница 15

MARS description

MARS (Modular Apparatus for nuclear Reactions Spectroscopy) is composed of detection, electronic, and acquisition systems. MARS electronics combine desktop and VME form factors. It is a portable and versatile spectrometer for measuring angular and energy distributions of charged particles outgoing nuclear reactions. Its modular and advanced design allows components to be exchanged (e.g. change detectors to measure different types of radiation), besides applying different types of digitizers, firmware, and then acquisition systems. In par ticular, the application of different firmware allows for different pulse analysis techniques.

Figure 1: MARS electronic system. It is based exclusively on desktop and VME form factors from CAEN SpA.

The detection system is composed of 16 semiconductor planar totally de plected silicon (Si) SBD (Surface Barrier Detectors) from ORTEC with active areas of 50 mm2. Eight of them have 15 µm thickness (model ED-35-050-15), and the other eight have 500 µm thickness (model TB-15-050-500) (nominal values). These detectors are suitable for the identification of charged particles and their respective high-resolution spectroscopy. The manufacturer specifies a resolution of 15 keV for 241Am alphas (5.486 MeV (corresponding to 85% of intensity)) [15, 16].

Figure 1 presents MARS electronic system. It is based on desktop and VME modules from CAEN SpA:

– TwoA1422 charge sensitive preamplifiers. They present a sensitivity of 90 mV/MeV (for Si detectors) and support a detector capacitance up to 200 pF (F2 type). The A1422 are implemented into alloy boxes, 8 channels each, and feature BNC connectors for the input (detector), SHV for high voltage supply, LEMO for the energy output and the input test (TEST IN), and a cable with a D – type 9 pin male connector for the power supply [17].

– The DT5423 power distributor provides 4 standard D-type 9 pin fe male connectors to supply up to 4 A1422 preamplifiers with ± 12 V [18].

An alternative VME form factor module [19] could be employed and inte grated in the same VME crate described below.

– Three V6519P HV power supply modules provide the high voltage (up to 500 V and 3 mA of voltage and current, respectively) to the de tectors. Each one houses 6 HV power supply channels that are controlled by software. The channels share a common floating return which allows on-detector grounding, reducing the noise level. HV outputs are delivered by SHV connectors [20].– The V1725S digitizer consists of 16 (0—15) input channels capable of recording waveforms (directly from the preamplifiers A1422 [17]) along with performing advanced algorithms for online DPP [21]. Using DPP f irmware, we are able to acquire the integrated charge and carry out PSD (Pulse Shape Discrimination) and PHA (Pulse Height Analysis), as well as read out waveforms with automatic pulse identification. It features 14 bit resolution, 250 MS/s sampling rate, and 2 V input range. This implies a digital precision of 0.12 mV and a digital resolution of 0.006%, with a processing time of 65 µs. Communication with the board can be done through the VME bus and Optical Link. It is well suited for mid fast pulses such as the ones coming from silicon detectors coupled to the charge sensitive preamplifiers A1422 [17].