More info about the MCA app required

Applications, development tools, FPGA, C, WEB
CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

More info about the MCA app required

Post by CJWestshore33 » Fri May 08, 2020 4:55 pm

I see a few years ago an MCA app (multi channel analyzer) was developed for doing gamma spectroscopy. I’d like to know more about it as info online is sparse regarding specs.

I need to output a .spe or .csv file so I can export to a spectroscopy processing application.

Also, does the app do isotope identification?

Thanks

pavel
Posts: 616
Joined: Sat May 23, 2015 5:22 pm

Re: More info about the MCA app required

Post by pavel » Fri May 08, 2020 5:35 pm

If it's about this application, then I could try to provide some additional information.

The default control program outputs the spectra in a format that looks like csv with an additional header:

Code: Select all

info {
start date: 
stop date: 02/02/2019 19:00:00
average rate: 0.00e+000 counts/s
total counts: 0.0
}
data {
0.0
0.0
0.0
...
0.0
}
The code writing the data is on lines 1033-1045 in mcpha.tcl.

The application only does the data acquisition. It doesn't have any data analysis functionality.

There are also several alternative control programs:

CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

Re: More info about the MCA app required

Post by CJWestshore33 » Fri May 08, 2020 5:58 pm

I am looking for a video or screenshots of this MCA program and
how it actually works. I need more info.

That’s great that the program is able to bring pulses in..
Is there a way of adjusting the gain for weaker signals?
Does it require an amplifier stage?

—- more info required either way.

pavel
Posts: 616
Joined: Sat May 23, 2015 5:22 pm

Re: More info about the MCA app required

Post by pavel » Fri May 08, 2020 6:40 pm

Here is a link to a screenshot:
https://github.com/pavel-demin/red-pita ... -568170900

The signal input requirements are similar to the requirements of other similar devices.

The MCPHA application works well with Gaussian-shaped pulses. Ideally, the amplitude range of the signal should closely match the hardware input range.

Red Pitaya 125-14 has two input voltage ranges 1V and 20 V. Voltage ranges are set by jumpers:
https://redpitaya.readthedocs.io/en/lat ... astIO.html

For example, if the voltage range is set to 1V, then the MCPHA application should be able to analyze pulses with amplitudes of about 5mV.

The minimal pulse duration should be around 5us.

CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

Re: More info about the MCA app required

Post by CJWestshore33 » Fri May 08, 2020 10:35 pm

I was under the impression that the RedPitaya was capable of 8nSec pulse capture.
If only 5uS, we are only talking about 320Ksps? I am a little confused. I will be using the board to process raw scintillation detector output from a LaBr3:Ce scintillation detector. These scintillators are quite fast --320-350nS pulse duration.... and very high resolution, second to only HPGe.

125Msps should be capable of at least 8nSec pulse length. :?:

CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

Re: More info about the MCA app required

Post by CJWestshore33 » Sat May 09, 2020 7:12 am

Just curious if anyone have a video of the MCA app running on the RedPitaya?

:?:

pavel
Posts: 616
Joined: Sat May 23, 2015 5:22 pm

Re: More info about the MCA app required

Post by pavel » Sat May 09, 2020 10:43 am

I was under the impression that the RedPitaya was capable of 8nSec pulse capture.
According to the specifications at this link, the input bandwidth is 40 MHz. I don't think this is enough to analyze 8 ns pulses.

Without a peak detector in front of the ADC, the pulse amplitude cannot be measured with reasonable resolution from just a single ADC sample. Depending on the resolution required, a few tens or even a few hundred ADC samples are normally used for the reconstruction of the pulse height.

More information on pulse shape analysis can be found in the articles linked from the very beginning of my notes at this link.
I am a little confused. I will be using the board to process raw scintillation detector output from a LaBr3:Ce scintillation detector. These scintillators are quite fast --320-350nS pulse duration
What do you mean by "raw detector output"? Is it the output of a photomultiplier or a charge sensitive preamplifier or something else?

What are the shape and amplitude range of these pulses?

I'd say that the 320-350nS pulse duration is too short to measure the pulse amplitude with reasonable resolution using Red Pitaya 125-14.

I developed the MCPHA application mainly for configurations with pulse shaping amplifiers with a shaping time of around 1 us or more (pulse duration of around 5 us or more). In this type of configuration, performance is quite reasonable and comparable to other similar devices.

CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

Re: More info about the MCA app required

Post by CJWestshore33 » Sat May 09, 2020 4:47 pm

The pmt signal will be going through a T-bias splitter off a
HV supply. So this is what is being used as a raw output.
I’m going to have to play around a with the input on the redpitaya... probably add a pulse stretching circuit to lengthen to pulse to the required minimum 5us.

pavel
Posts: 616
Joined: Sat May 23, 2015 5:22 pm

Re: More info about the MCA app required

Post by pavel » Sat May 09, 2020 5:49 pm

The pmt signal will be going through a T-bias splitter off a
HV supply. So this is what is being used as a raw output.
I'd say that if you send the current pulse from the photomultiplier directly to the Red Pitaya input, the noise performance of this configuration will be rather poor.

I'd suggest adding at least a charge-sensitive amplifier that would integrate the current pulse from the photomultiplier. It can be built from an operational amplifier with JFET input (OPA656, OPA659, LTC6268).

I've just found a few posts with some relevant schematics:
http://physicsopenlab.org/2016/04/21/pm ... rocessing/
http://physicsopenlab.org/2017/06/22/x- ... hotodiode/
http://physicsopenlab.org/2017/09/27/ch ... amplifier/
http://physicsopenlab.org/2019/03/26/mi ... amplifier/

CJWestshore33
Posts: 29
Joined: Sun Dec 07, 2014 5:41 am

Re: More info about the MCA app required

Post by CJWestshore33 » Sun May 10, 2020 5:55 pm

Yes, actually going to try a number of experiments with the Red pitaya and your MCA app... excited.
In terms of the charge sensitive amplifier, I will probably look at the Micod PMT charge sensitive-preamp as it has been recommended several times in the past. Good thing you reminded me about this! Thank you for letting me know about the actual sampling rate --- the quoted 125Msps is only possible under what conditions? I guess that is my misunderstanding is.


Another question however is if is be possible to send the incoming data over USB or Rs232 from the to be picked up on both the open port of BeqMoni and RH Electronics MCA terminal. :idea:

-- I'll have to pull data from the Rpitaya somehow.

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