DSP based MCA (Multi-channel Analyzer)Sharon Rose Swamikan | Dr. S. Kumaravel | SENSE

Objective

Results

Methodology

1. Study of various pulse shaping and processing methods:

• Triangular

• Trapezoidal

2. Use of digital processing techniques and its and its implementation in pulse processing to give better spectroscopic performance.

MCA is the heart of nuclear spectroscopy. A common application in nuclear science for the MCA is the radio isotope spectroscopy, in which particle energy is estimated. A DSP based MCA is developed for this purpose. Particle identification is done by the electrical signal which is produced the interaction of the gamma ray with the detection medium. Various shapers like the triangular and trapezoidal are studied and compared. Digital processing techniques are implemented to give better spectroscopic performance.

Introduction

References[1] Selected topics in nuclear electronics" IAEA, Vienna, 1986 IAEA tecdoc-363, 1986.[2] P. Soo, C. Sik, and J. Hahn, “Development of FPGA-based digital signal processing system for radiation spectroscopy,” Radiation Measurements, vol. 48, 2013.

Conclusion

Contact Detailssharonrose.swamikan2014@vit.ac.in

FALL TIME 8-STANDARD DEVIATION

16- STANDARD DEVIATION

32-STANDARD DEVIATION

1 ms 3.76 1.98 1.22

500us 3.80 1.95 1.21

200us 3.80 1.98 1.19

100us 3.81 1.97 1.17

50us 3.82 1.98 1.19

20us 3.81 2.01 1.1910us 4.11 2.02 1.32

5us 4.11 2.02 1.32

2us 4.16 2.01 1.32

1us 4.14 2.01 1.30

FALL TIME

12-STANDARD DEVIATION

20-STANDARD DEVIATION

36-STANDARD DEVIATION

40-STANDARD DEVIATION

1 ms 1.82 1.61 1.74 2.16

500us 1.78 1.63 1.82 0.71

200us 1.76 1.38 1.69 0.73

100us 1.76 1.45 1.67 0.71

50us 1.77 1.46 1.52 0.70

20us 1.77 0.98 1.79 0.69

10us 1.91 0.84 1.66 0.69

5us 1.90 0.82 1.65 0.74

2us 1.90 0.85 1.68 0.71

1us 1.89 0.84 1.44 0.75

Table 1.Triangular shaper results

Fig. 3 Histogram and fit curve of 32rd order triangular filter with 1ms fall time

Table 1.Trapezoidal shaper results

Fig. 4 Histogram and fit curve of 40th order trapezoidal filter with 1ms fall time

• Trapezoidal filter has the advantage that the peak stays for a longer time so that there is less chance of missing the peak compared to triangular filter. • The output resolution of trapezoidal filter is having almost 50% less noise than that of the triangular filter. • No. of multipliers in case of trapezoidal filters is less than in case of triangular filters• The time constant variation study is done to find out the rate capability of the filters and how it degrades with fast fall times.

• Traditional analog spectroscopy performs shaping on analog data thereby having a long analog chain.• Digital spectroscopy reduces the analog chain and digitizes the CSA out directly. • Shapers like Gaussian, triangular, trapezoidal , flat top cusp are been using in the spectroscopy process.• HPGe detectors are used as they give highest resolution.• Spectroscopy systems are designed with pile up detection and rejection , baseline restoration. • Various triggering methods are studies and simulated like the leading edge and the CFD.• The histogram and Gaussian fitting of the curve gives details about the particle and amount of particle emitted.

Input generation

Analog to digital conversion

Filtering process

Plotting spectrum

Fig. 1 Triangular filter simulation

Fig. 2 Trapezoidal filter simulation