NCP-Centre of Excellence, National Centre for Physics,Islamabad,Pakistan

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Resistive Plate Chambers

RPC Testing Procedure

PAEC is responsible for the assembly of RPCs (Resistive Plate Chambers). In order to keep up RPCs' quality during assembly process, following pre-assembly and post-assembly tests are done at PAEC.

Gas Gaps Testing
Visual Test Check the dimensions of the gas gaps at random positions Note down the buckling of the gaps and reject gaps bent more than 8mm Check the gas inlets, HV and ground connections for any damage Store gas gaps which pass initial visual test under humidity and temperature control area
Leakage Test Block two inlets of gas gaps and connect other two inlets to the gas system and manometer respectively Keep the gap under 20-mbar over pressure for 10 minutes and observe reading on the manometer Reject the gap, if the pressure column on the manometer is reduced by 2 cm after 10 minutes
Spacer Test Place a template sheet where each spacer location is marked on the gas gap Note the height of water column in the manometer after 10 minutes of 20-mbar of over pressure in the gas gap Press each spacer twice (5 N force at least) and check the water column of the manometer. If there is a sudden jump of about 1.5 -3 cm then that spacer is a pop spacer Note this information in the gas gap test check list
High Voltage vs. Dark Current Test Place gaps under high voltage with the gas mixture (Freon 95% and Iso-butane 4.5%) under 2 mbar pressures at 5 l/h for 8-10 hours Measure the dark current. Accept the gaps with less than 5-6 µA currents for the assembly Note the high voltage and dark current and plot the graphs Save the data and plots in the database Perform all the tests under humidity and temperature control. Save the temperature and humidity readings in the database
Other Quality Control Tests

FEB Boards Testing Test the FEB boards in the testing jig provided by Matrix, Srl , Italy Store all the data for each FEB board in the database
Gas Pipes Bending Bend the gas pipes with the help of jigs to follow the proper routing inside as well as outside the chamber. Heat the gas pipes with a controlled heating plate and then put in the cold water. The time duration for heating of each shape may vary. Monitor the process closely After heating the gas pipes must not have any kinks Blow the prepared gas pipes with the dry air to remove moisture or any dust particle in the pipes
Coolant Pipe Pressure Test Block one end of the pipe and connect the other end to the oxygen cylinder with pressure regulator Gradually increase the pressure up to 20-bar and maintain it for 5 minutes Use soap solution to check for any leakage at joints and brazing ends
After assembly, the chambers are moved from PAEC to NCP for further testing and quality assurance using cosmic telescope. Following tests are performed at NCP.

Visual Inspection All chambers are inspected visually, refer RPC Quality Assurance Sheet
Testing using Cosmic Telescope

Use gas mixture consisting of 96.5% Freon, 3.0 % Iso-butane, and 0.5 % SF 6 Apply the high voltage after 8 volume changes Gradually raise HV to 8.6 kV. Leave chamber for 6 hours and note the dark currents at regular time intervals
High Voltage Scan Perform HV scan with the following HV points:: 8600, 8800, 9000, 9200, 9300, 9400, 9500 & 9600 V Take 20,000 events for each HV point. Use offline analysis program to calculate the following chamber parameters: Dead and Noisy Strips Efficiency Cluster Size Rate Probability of Spurious Hits Record all results on a sheet as well as in the database. Reject the chamber, if the measured efficiency is less than 95% or the cluster size is bigger than 3 at the nominal operating voltage of 9300 V

RPCs Testing Status