Radioactive source and cosmic-ray test for the MWPC Davide Pinci on behalf of the Frascati-Roma1 MWPC group

Davide Pinci Outline At the end of the construction process we plan to perform a quality control of the Multi-Wire Proportional Chambers. For this purpose we built: A table to investigate the gain and its space uniformity by means of a radioactive source of each gap of the chamber; A cosmic ray station to study the chamber total efficiency and time performance; The large number of chambers produced demands: Fast and automated test setup fully controlled by PC; Organized data storing;

Davide Pinci Test with the radioactive source The measure of the gain of each chamber gap is performed by means of a radioactive source; It results to be a very usefull test: Th chamber can be tested whitout front-end electronics; The measurement is very fast: the whole chamber can be checked in less than 1 hour; The gain uniformity provides important information on the quality of each gap: gap thickness, wire spacing, electrical connections, gas flow uniformity; The gain absolute value provides information on: uniformity between the different chamber gaps; uniformity in the chamber production (once corrected for the room temperature and pressure variations);

Davide Pinci System set-up We use a 137 Cs source; The current drawn by each gap is measured by a nano-amperometer built in Frascati, providing 1 nA of resolution; The source activity is about 40 mCi which means a production of about ,662 MeV photons/s over 4  (about over a 24° cone); With the nominal chamber gain ( ) a current of about 70 nA is expected; The source is shielded in a lead case which insures a dose rate lower than 0.5  1 m far from the source. 137 Cs source Lead case

Davide Pinci The measurement table Two stepping motors control the source movement in the two directions; The motors are fully controlled by PC via an I/O National Instrument board (6025E) and a driver; The position precision is about 0.5 mm for both axes.

Davide Pinci Gain uniformity requirements The main requirements on the gain uiformity are related to the working point. Quoting the EDR: “If G 0 is the nominal gas gain, we want the gas gain in 95% of the area of a single gap to be within G 0 /1.25 and G 0 *1.25 i. e. between 0.8G 0 and 1.25G 0. The remaining 5% of the area should have a gain within a factor 1.5 i.e. between 0.67G 0 and 1.5G 0 ” Since the gain double each 106V, this requirements allows to have almost the entire chamber efficient by working 50 V (30% of the gain) above the nominal value of 2530 V: HV = 2580V 2530 V

Davide Pinci Chamber C001

Davide Pinci Chamber C002

Davide Pinci Comments Chamber 01: For the 4 gaps: 93->99 % of the gap area in the required range; Chamber 02: The gaps 2, 3 and 4 show very good gain uniformity: 96 ->99% of the gap area in the required range; gain distribution r.m.s. resulted about 10% of the average values; The gap 1 shows two different gain regions; It can be due to a not perfect panel planarity. Nevertheless the 76% of the area is within the required range and the 90% is in the range 1/1.30 and 1.30; The gain distribution r.m.s. resulted to be the 18% of the average gain value. All the 4 gaps have 100% of the area in the range 1/1.50 and 1.50.

Davide Pinci We plan to study MWPC efficiency, time performance and cross-talk; 6 MWPC layers are tested at the same time in order to shorten test duration and to perform muon tracking; With this set-up the chamber edge performance measurement will be the most time consuming; The cosmic ray test station Lead layer for shower veto Trigger is given by 3 scintillators with double read-out: a total efficiency of 90% and a time resolution of ~1.8 ns were measured.  100  400 PM

Davide Pinci Test performance We plan to investigate the performance of each physical channel; MWPC will be equipped with a readout circuitry: ASDQ or Carioca We made some simulations to evaluate the time needed: Test time is expected to be less than required by the MWPC production rate; Number of channels input into a multi-hit 128 ch TDC (CAEN V767) reduced via dedicated circuitry: multiplexing boards to reduce cost.

Davide Pinci Channel multiplexing To multiplex many channels from the MWPC FEB into a reduced number of TDC channels, groups of FE channels are delayed as shown in figure.  t needs to be larger than the MWPC time resolution in order to prevent a biased measurement. Channel group 1 tt tt tt tt tt tt tt tt tt tt Ch2Ch2 Ch4Ch4 Ch5Ch5 Ch3Ch3 Implementation is on an FPGA. Signal lines can be propagated through long cascades of gates used as delay lines;  t can be selected in the range ns; Lab measurements show jitter values below 400ps over the allowed voltage and temperature operating ranges.

Davide Pinci Muon station set-up situation The station mechanics drawing and materials are ready and the station construction is foreseen by the end of december; Scintillators, PMs and electronics for data acquisition are set-up; DAQ system (Labview based) already written and working in Roma1 university; Plan to debug the whole system (without Mux) by testing some MWPC prototypes as soon as the mechanics is ready; The MUX: All the material and components are in Roma1 The electronics drawings are ready and the board layout is arriving The whole system should be working by the end of Feb 04 In the meantime we plan to test the chambers by using more than one single TDC.

Davide Pinci Time, manpower and conclusions Radioactive source test: The whole system (gas, HV, source-positioning, current readout) is working properly; 1 hour and 1 person is needed 2/3 times per week for the test; Cosmic-ray stand: Now: Trigger and data acquisition are ready in Roma1; Dec 03: debug (in Roma1) with some MWPC prototype; Jan 04: set-up in Frascati and start of tests with a preliminary version (without Mux); Feb 04: Mux arrive and cosmic stand up-grade; 1 person needed fulltime.