MASS SPECTROMETRY SYSTEM FOR THE LEAKAGE CONTROL USED FOR MUONS DETECTORS FABRICATION IN THE ATLAS-CERN EXPERIMENT  - Leakage-Control

 

International partners:

 

Funding: Romanian funds for involvement in the Joint Institute for Nuclear Research, Dubna, Russia

 

Coordinator: INOE 2000, Romania, RO Project manager: Dr. Viorel Braic

 

OBJECTIVES

 

STAND FOR  MDT  DETECTORS  MANUFACTURING in JINR Dubna (Russia

The system of muon detectors in ATLAS-CERN consists of 400.000 tubes filled with a mixture of Ar (92%), CH4 (3%) and CO2 (5%) at an internal pressure of 2 atm.

A radio-frequency mass-spectrometry based leak detection system (LDS) for the in-line checking of aluminum tubes and detectors for MDT chambers mass production was developed and operated.

Leak Detection System (LDS) - designed to be used in the quality checking to ensure that the lifetime of the system corresponds to the requirements of the end-user. It fulfills the specific requirements for mass production:

                - short test time (< 5 min.);

                - leak rates in the range: 10-4 - 10-7 mbar.l/s;

                - minimum flow rate yet detected is 10-8 mbar.l/s.

                - accuracy of 10%;

                - automated operation;

                - automatic data acquisition and storage;

                - simple maintenance.

 

RESULTS

The leak detection stand consists of:

•              mass spectrometer gas analyzer consisting of radio-frequency mass spectrometer (MS) type  RGA 100 (Stanford Research Systems) and vacuum system (VS);

•              test bench with Al tubes/detectors supports, including end connector devices for Al tubes/detectors ;

•              test gas mixture (compressed air and He) preparation station;

•              computer (PC), control block (CB), accessories, and software.

 

 

Block diagram of leak detection stand LDS

Automated procedure for the Al tubes leak detection

1. put a tube on the bench;

2. assign a number for the tested tube in the computer;

3. shift gently the tube in the immobile connector and fasten it;

4. shift the blind connector over the other end of the tube and fasten it;

5. press the TEST push button and an automatic sequence starts. The  START/STOP green and red LEDs will flash till the pressure value at the entrance port of the spectrometer reaches the level set before. Then the green LED remains lit.

6. spray He - air mixture on the external wall of the tube (between the end connectors), using the test pistol;

7. the computer will display the partial pressure of helium versus time. The operator has to decide the quality of the tested tube by comparing the displayed level of helium partial pressure with the set level.

8. the operator has to write test data in the Leak_Data software.

9. when the test is finished, press the “TEST” button. The   LED “TEST”  is lit and the red color change to green colour.

10. press the air admission “AIR ADM” button to pressurize the tube and loosen the end connectors.

 

Leak detection procedure for chambers

The chamber was tested after the detectors were assembled, assuming that the detectors were not damaged during this operation. Only the end plugs and plastic connectors will be tested.

The detectors will be filled with the test gas mixture (air + 10% He) and the test was carried out using the sniffer probe.

The sniffer probe was connected to the test port of the mass spectrometer.

During this test, the vacuum system including the mass spectrometer is maintained in the “TEST” mode.