Cosmic Ray

[Wojtek]

Lodovico:
I am running with Tom's detector now. The test run yielded many background events, but with enough time the true meson decay will build up. Preparing for this, I ran for 3 days with a 3" by 4" NaI(Tl), which has higher stopping power than plastic. The results are posted on my website http://www.FemtoDAQ.com, under the tab "Measurements with vacuum PMT" (the 2nd tab from the right). The decay curve is very apparent. The fitted tau was 1.93 microsecond.

[lodovico]

Very nice results, with the plastic scint maybe you have to put a higher threshold.
Very interesting your femtoDAQ !!! It is just what I need for many of my projects (with SiPM also). I did some hardware but yours is far better than mine ! Can I ask you some information (price also) about it ? You can write me at this email : lodovicolappetito@gmail.com
Thank you
Lodovico

[Wojtek]

Lodovico:
Thank you! Yes, the higher threshold will do it. I will apply higher threshold offline. Since Friday FemtoDAQ is writing the event file with the waveforms. I will close the file on Monday and process offline. Since there is a full waveform for every event, I can integrate the pulses and threshold them. Here is the example.

Double_pulse.png (3.11 KiB) Viewed 11472 times

Expanded_baseline.png (3.39 KiB) Viewed 11472 times

Another nice feature is low noise of this 14-bit digitizer. Look at the same waveform expanded around the baseline. The RMS noise is about a single LSB. We originally developed this electronics for the Homestake cryogenic experiment which is looking for Dark Matter with liquid xenon. The FemtoDAQ is an offspring of that project. I can say (with modesty) that one cannot find better nuclear physics electronics anywhere. I am saying so because we are just at the limit of what the ADC can do.

[lodovico]

Yes, it looks impressive, both the low level of noise and the time resolution, it must be a really good equipment !
Lodovico

[Wojtek]

Setup_overview_small.jpg (69.68 KiB) Viewed 11454 times

Legend: A) HV - signal splitter. B) HV supply. C) FemtoDAQ. D) iRad detector (3 inch BC412). E) FemtoDAQ control.
Many thanks to Tom for the detector and the splitter box!
Here Is the result after 4 days of running. The statistics:
Total processed events= 3,512,000, written to disk= 8551, events with multiple pulses= 1531

BC412_Decay_curve_with_fit.png (5.58 KiB) Viewed 11454 times

After fitting, I found 554 muon decay (the integrated exponential part of the histogram).
The fraction of "true decay" / "all double" = 554 / 1531 = 36%.
The fraction "true decay" / "all events" = 554 / 3512000 = 1.577e-4.

[lodovico]

Nice results and nice hardware also. It took me weeks to collect, manually with the oscilloscope, 400 events, not 4 days ...
I think that to have a better exponential fit, with a good "binning", it is necessary to collect thousands events, otherwise you can use the statistical method MLE to get an esteem of the muon lifetime.
Lodovico

[Wojtek]

Lodovico:
thank you for the hint concerning the fit. All this is a fun project for me. I analyzed this data in about one hour while listening to a video conference on our new "big science" project ;-) Seriously, this instrument is highly automated. The data collection and event selection is performed by a python script. It runs unattended. This time I prescaled the single-pulse events by 500. The same event file records every double pulse, and every 500th single pulse to gather a representative sample of the latter. (I will analyze this portion of data during the next teleconference ;-). I wrote the data analysis code in IGOR. It is perhaps 2 pages long. Processing the event file takes less than a minute. Then editing and captioning the figures takes half an hour. I can perform many fun experiments in a short time. Hopefully some colleges and maybe even high schools can adopt our instrumentation for the benefit of educating students in nuclear science.

[iRad]

Hi Wojtek - Nice work! It's very interesting to know that good science can be even achieved with a good 3 inch plastic scintillator. I'm looking forward to seeing what you do with the second detector and the dual detector splitter box I just sent you. Thanks for the pictures and the mention. It will be really nice to see this kind of processing power inexpensively available to the education market and hobbyists. Cheers, Tom

[Wojtek]

Hello everyone:
I have created a new website CosmicRayNet.net. I posted a detailed description of a cosmic ray run using iRad plastic detector. Many thanks to Tom for the wonderful detector. I have ideas for more cosmic ray experiments. I wish I had time to work on this asap.

Yesterday I presented the experiment to grad students and High Energy Physics faculty at the University of Rochester (Rochester, NY). They were impressed both with Tom's workmanship and the price of the detector unit.
Cheers -- Wojtek

[lodovico]

Hi,
yes, the Tom's plastic detectors plus the FemtoDAQ are really interesting for schools and for hobbyists.
A question for everyone : is there someone who can provide slices of plastic scintillator ? I mean a square with these dimensions more or less : 5cmx5cmx1cm, in order to couple it with a SiPM at the side.
Thank you
Lodovico