MAPIC : Multichannel Analysis and wireless DAQ  for the APIC

In the context of a summer student project, a multi-channel analyser (MCA) function was added to the existing APIC preamplifier-shaper-trigger box developed for the GDD lab (Fig. 1 left).  For this purpose the fast, semi-gaussian shaper signals of the APIC get stretched by a custom peak-finder & stretcher card. At the output of the stretcher, the peak level of the  25 ns shaper signal is kept constant for up to 2 µs to get digitised by a 2 MSps ADC  embedded in a MCU with a Micropython interpreter. The digitised peak data are transmitted wirelessly to a Laptop for online histogramming. A Tinker GUI was developed for controlling  parameters such as gains, thresholds and signal polarity.

Left: (M)APIC box with pre-amplier-shaper-stretcher card, HV bias generator, MCU plugin card and wireless antenna. Inset: stretched pulse. Middle: MAPIC Controls via GUI. Right: Bragg histogram of 241Am with a pin diode connected to MAPIC.


As proof of principle, a pin-diode was connected to the APIC pre-amplier input to record Bragg  histograms  of an  241Am  alpha source as shown in the right plot in Figure 1, which agreed well with literature spectra. 55Fe energy spectra from a  GEM detector were acquired  at  rates of up to 2 kHz with wireless data transmission. The  ratio of main and escape peak positions closely matched the nominal value of 2:1.

HAL  libraries  were used to to interleave 3 ADCs and increase sampling rates to 7 MSps. The C code was optimised for DAQ rates targeting up to 100 kHz. The MAPIC project and associated software was archived at Github  in order to be resumed in 2020 for full commissioning and production.

Setup in the GDD lab: GEM detector and (M)APIC accumulating 55Fe spectra.