A fast filter processor as a part of the trigger logic in an elastic scattering experiment
✍ Scribed by I. Kenyon Gjerpe
- Publisher
- Elsevier Science
- Year
- 1981
- Tongue
- English
- Weight
- 843 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0010-4655
No coin nor oath required. For personal study only.
✦ Synopsis
A fast special purpose processor as a part of the trigger logic in an elastic scattering experiment is described. The decision to incorporate such a processor was taken because the trigger rate was estimated to be an order of magnitude higher than the data taking capability of the on-line minicomputer, a NORD 10. The processor is capable of checking the coplanarity and the opening angle of the two outgoing tracks within about 100 ~s. This is done with a spatial resolution of 1 mm by using two points along each track given by 3 MWPCs. For comparison this is two orders of magnitude faster than the same algorithm coded in assembly language on a PDP 11/40. The main contribution to this increased speed is due to extensive use of pipelining and parallelism. When running with the processor in the trigger, 75% more elastic events per incoming beam particle were collected, and 3 times as many elastic events per trigger were recorded on to tape for further in-depth analysis, than previously. Due to major improvements in the primary trigger logic this was less than the gain initially anticipated. A first version of the processor was designed and constructed in the CERN DD division by J. Joosten, M. Letheren and B. Martin under the supervision of C. Verkerk. The author was involved in the final design, construction and testing, and subsequently was responsible for the integration, "programming" and running of the processor in the experiment.
1. The experiment
angle. The low elastic cross-section results in a very low ratio of elastic events to total triggers.