RPC Atlas – Stato del progetto Riunione Commissione I 13 Maggio 2003 By R. Santonico

Stato della produzione Feed back del test con RC delle unità BML-D Test su camere con distanziatori non incollati Risultati attuali del test di invecchiamento alla GIF su camere di produzione Valutazione dei costi a completamento del progetto

Production status

The production rate of the read out panels and units assembly is now above 2 units/day and is approaching the limit of 3/day However there is now some problem in the support panel production (Protvino) which has to be very quickly solved

Feed back of the BML-D chambers CR test Gas volumes analysis: - Most of the problematic gas volumes had been discarded or suspended in the current test. They were erroneously used in the chamber assembly (the current test had been just introduced and some feed back did not work in our organization) - Some of them were found to have significant leak currents at the edges >>> improve the edge sealing - A few shown small areas of lower efficiency (while having good average efficiency)

Feed back of the BML-D chambers CR test (2) Read out panels analysis - 3 panels were found with a die damaged during the chamber assembly >>> improve accuracy in handling the panels - In other 3 cases the problem was due to mistakes in the panel assembly - However in a significant number of cases, panels indicated as problematic and dismounted were found to be good >>> possible mistakes in the test, for example wrong connections to the output cables A new test has been introduced to detect read out panel problems before the CR test

Chamber performance around unglued spacers A BML-D unit was purposely assembled using gas volumes that had been rejected by the punch test for having a very large number of unglued spacers The standard CR test did not show local inefficiencies at the position of the unglued spacers proving that the Atlas RPC mechanical structure is capable of compensating for possible unglued spacers

Improvements in the procedure After the first large scale testing of production chambers, two main improvements have been introduced in the construction/assembly procedure Improved gas volume edge sealing The edge is now sealed using a “C” profile of 190 microm thick PET, the same already used for the isolation of the graphite electrodes At the end of the chamber assembly a new QC test is made to check the integrity of all read out panels These improvements are expected to strongly reduce the rate of units which do not pass the CR test. The next series of units produced, BML-A, already includes these improvements. CR test results should be available in a few weeks

Status of the ageing test at X5 The test is going on continuously and is now reaching the limit of 3 Atlas years (90 mC/cm2) including the safety factor of 5-10 The gas closed loop system has been mounted and will be gradually introduced for 4 out of the 6 detector layers that are under test. The other two will remain in open flow Detection efficiencies are good A modest increase of the source off current is observed In July and August the set up has to be removed from X5 for MDT testing >>> long time required for reaching the limit of 10 Atlas years

Efficienza vs HV

Valutazione costi a completamento del progetto Sistema gas (residuo) 220 kE Cavi connessione FE – Trigger 160 “ La preparazione dei cavi richiederà anche un adeguato impiego di mano d’opera (esterna, fondi FAI?) Sovracosti di produzione gaps (scarti + ricambi) 400 (Max) Sistema di potenza A fronte di un totale di costi residui valutabile a 1780 kE la parte di core ancora disponibile è di 980 kE con una differenza di – 800 kE