From: Ger van den Engh (engh@biotech.washington.edu)
Date: Wed Apr 12 1995 - 16:08:51 EST
The experiments (Langlois, van den Engh) mentioned by Thomas Delohery were obtained with a data acquisition system with a cycle time of 5.5 microseconds. This means that the system can accept events at a nominal rate of about 180,000/s. In this time the system measured 8 parameters and compared the data to four 256 x 256 bit lookup tables. This system evolved into the present MoFlo electronics that can do 32 parameters and 16 lookup tables comparisons within a cycle time of 6 microseconds. At this speed of data collection and sort decisions, the computer can not keep up with the data stream (we used an HP320 at the time). It is impossible to store data at a rate of 12 Gbyte/s. Our solution was to filter the data and send only data of interest to the computer. This was done by gating the computer interface with the output of the sort lookup tables (a feature originally built by Willem Stokdijk). Only events falling inside the sort windows are send to the computer. Since Rich Langlois was interested in rare mutant cells he could weed out the majority of the non-interesting, normal cells and only store the potential mutant cells as raw data list. With the gated interface we analyzed at rates of 40,000 cells/s and store 2000 of those that were of interest. The 2000 events/s that were collected were stored as data lists of 8 parameters. Therefore multiple hstogram displays could be obtained for the stored cells. The acquisition system was tested on a FACscan and allowed datacollection at fairly high rates without missing the important cells. (I forgot the exact numbers but it reached ten thousand/s at times). The collection rate of the facscan with the custom electronics was significantly higher than the native facscan rate. This indicated to us that under normal operation the facscan is limited by its data acquisition system rather than the combination of sample velocity, core width and excitation spot size. I believe that Rich is still using this system although I'm no longer aware of the exact details. Hope this info is useful. Ger
This archive was generated by hypermail 2.1.6 : Thu Jan 01 2004 - 17:30:30 EST
