| Alan Stummer
Research Lab Technologist
PhotonFinish2 - Octal Coincidence Timer
I am curious who uses what. Are these webpages a waste of time, or are they any help to others? Are the circuits, software and utilities appearing in other labs? Please send your comments or suggestions or what you have used (or not) or schematics of your version or pictures or anything! Email me, or be creative and send a postcard! I want to hear from the vacuum!
NOTICE: This webpage and associated files is provided for reference only. This is not a kit site! It is a collection of my work here at the University of Toronto in the Physics department. If you are considering using any schematics, designs, or anything else from here then be warned that you had better know something of what you are about to do. No design is guaranteed in any way, including workable schematic, board layout, HDL code, embedded software, user software, component selection, documentation, webpages, or anything.
All that said, if it says here it works then for me it worked. To make the project work may have involved undocumented additions, changes, deletions, tweaks, tunings, alterations, modifications, adjustments, waving of a wand while wearing a pointy black hat, appeals to electron deities and just plain doing whatever it takes to make the project work.
For Xingxing Xing, Lee Rozema and Dylan Mahler in Aephraim's lab, started Nov 2010. A new and improved version of the original Coincidence Timer - PhotoFinish which had 2 channels and 50pS resolution, this one has 8 channels with 81pS resolution.
Probably the largest change is how the timing is measured. In the original PhotoFinish, ADCs measured RC slopes with an FPGA to capture the raw data, then that was sent to the host which converted those asynchronous events to relative timing. In this new version, the PhotonFinish2, timing is done with Acam's TDC-GPX series of time-to-digital converters.
The whole system has been overhauled. Besides possible processing limitations even with an ARM Cortex A9 CPU, the bottleneck was getting data from the unit. Ethernet would be limited to approximately 1.5M events per second, and that is at 100% utilization. Although Firewire or USB are faster, they are not fast enough. The decision was made to use a PCI-Express card inside a computer. The basic board is an Altera Arria II GX development kit with a custom HSMC (High Speed Mezzanine Card) board with the Acam IC.
Details to follow...
|Please direct questions, queries, broken links, problems, flak, slings, arrows, kudos, criticism, comments, brickbats, corrections and suggestions to astummer_at_physics.utoronto.ca.|