USBMCA-2.0 records an energy spectrum over USB. Hardware variants cover 1K to 32K channels. Plug in BNC, feed a shaped pulse, and acquire in list mode — on the desk, in the browser, or from a short Python script.
Instrument
USBMCA-2.0 is a compact USB instrument for scintillation spectroscopy. Connect a shaping amplifier to the SHA input, set the threshold, and build a spectrum on the host — live Gaussian fits included. Channel count is a firmware variant: 1K, 2K, 4K, 8K, 16K, or 32K.
| Model | USBMCA-2.0 |
|---|---|
| Channels | 1K–32K variants (1024, 2048, 4096, 8192, 16384, 32768) |
| Input | SHA pulse, 0–5 V |
| Conversion | 16-bit ADC |
| Acquisition | List mode (pulse-height list to the host) |
| Threshold | 12-bit lower-level discriminator, software-set |
| Power | USB powered, portable enclosure |
| Software | Linux desktop app · Chrome web app · Python library |
Each pulse height is digitised at 16-bit resolution so photopeaks stay well sampled across the 0–5 V SHA range. The firmware maps that conversion onto 1K–32K PHA bins depending on the variant.
Events are streamed as a list of pulse heights. Histogram is generated on the host in real-time, including on the fly analysis.
A 12-bit lower-level discriminator, and 3 spare channels for HV adjustments, and other needs.
Shaped analog pulses from a spectroscopy amplifier. Unipolar SHA in the 0-5 V window [the usual output of a scintillator + PMT or SiPM chain] with 3us rise time.
No extra power brick. One cable to the computer (or a phone, via the web app) is enough to run the analyzer.
Histogram GUI for Linux, Chrome WebUSB on desktop or Android, and a Python library for scripts and overnight runs.
Host software
The desktop GUI and the Chrome web app share the same workflow: record, clear, live analysis, energy calibration, CSV export.
Applications
An MCA measures the height of each pulse and builds an energy spectrum. With a scintillator and a shaping amplifier, that spectrum is the language of gamma rays.
Photopeak, Compton continuum, and backscatter from NaI(Tl), CsI, or LaBr3. Identify 137Cs (662 keV), 60Co (1173 / 1332 keV), 22Na, and mixed sources.
Undergraduate nuclear physics: energy calibration, FWHM vs. energy, coincidence setups, and counting statistics — without a crate of NIM modules.
Resolution (FWHM), peak-to-Compton, and gain drift. Live fits update every second so you see the effect of HV, threshold, or shaping time immediately.
Count-rate and spectral fingerprints for lab sources, shielding checks, and teaching-scale environmental or food-sample demos.
Any shaped unipolar pulse into the 0–5 V SHA input. Useful for scintillator work, SiPM gain curves, and X-ray fluorescence with a suitable detector.
The Python library is not tied to the GUI. Log spectra overnight, set the threshold from a script, and write CSV from a notebook.
Download
Package usbmca 2.0.0 for USBMCA-2.0 installs the histogram app, USB permissions, and a desktop launcher. The host reads the firmware channel count (1K–32K) on connect.
sudo dpkg -i usbmca-2.0.0.deb
sudo apt-get install -f
No install on desktop Chrome. On Android, use HTTPS and grant USB access when prompted.
Run usbmca from the menu or a terminal. Headless library: from usbmca import MCA.
Library
Installed with the Debian package as usbmca.
from usbmca import MCA import time with MCA() as mca: mca.clear() mca.set_threshold(200) # 12-bit threshold mca.start() # list-mode acquire time.sleep(10) n = mca.get_counts() spec = mca.histogram.copy() mca.stop() print(f"events={n} peak_bin={spec.argmax()}")
Resources
Connect USB, attach a 0–5 V SHA pulse, install the desktop package or open the web app, then press RECORD. The installer sets USB permissions on Linux.
Desktop Chrome can use the histogram app with no extra software. On Android, Chrome needs a secure (HTTPS) page before it will talk to the USB device.
After installing the package: from usbmca import MCA. Start list-mode acquisition, set the 12-bit threshold, and read the histogram or event count from a script.