Report of the discussion meeting on the third arm for hall A on November 8, 1997.

There are various ideas in the community for additional detectors in hall-community which are fed by the wish to detect other particles than only protons or to measure more exclusively, i.e (e,e'gammagamma), (e,e'n) and (e,e'pp). Each of these potential experiments has its own requirements on scattering angle, distance to the target, energy of particle to be detected etc. On the other hand it is clear that this third arm will in general determine the luminosity at which the planned experiment can take place. During the discussion we have looked for common points of interest. Below follow the agreements that have been made.

Ed Brash will setup an HallAThirdArm mailing list.

** note from Ed: You can send a message to everyone on this list by sending it to

The following detectors are candidate to be tested (all dimensions are given as height x width x depth and in cm's):

The following 6 persons have agreed to play an active role. This HATA task force consists of Ed Brash, Shalev Gilad, Bill Hersman, Eddy Jans, Richard Lindgren and Bogdan Wojtsekhowski.

** note from Ed: You can send a message to these six people by sending it to

It was agreed upon that those who are interested in obtaining certain count rates should specify their favorite experimental conditions like angle, absorber, threshold, distance to the target etc., and mail this to Ed Brash before November 24.

Ed Brash will make an inventory of the proposed tests and mail this around.

Pavel Degtiarenko will make then predictions for the one or two tests we decide to start with.

A system should be set up that contains electronics and DAQ + analysis software, such that HVs and thresholds can be set, ADC and TDC information can be obtained. Spectra must be produced, cuts be set etc. Also scaler information must be easily obtainable. In this way we will be able to investigate parasitically the response of some detectors while two-spectrometer experiments are running in hall A. Next some specific dedicated tests being the main user can in principle be scheduled.

Looking forward to a pleasant and fruitful collaboration,


eddy jans

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11/14/97 / Eddy Jans Greeting Message / Last Updated 2/26/99