Beam positions AB RB 1 chamber positions in

Beam positions (A-B) RB 1 chamber positions in the GIF area source B beam A 3. 5 m Operation condition at the GIF at ABS 1: Photon flux at ~3. 5 m : Sensitivity to 662 ke. V photons: backward Aging position Cham 25 Cham 26 Hit rate: Rate is lower due to other detector in front of the chambers In the beam position the chamber are ~20 cm nearest to Higher the source and some detectors has been removed counting rate

Accumulated charge 0. 0198 C/cm 2 Chamber 25 0. 020 C/cm 2 Charge C/cm 2 Chamber 26 12 June A lot of charge has been integrated in last month (higher operating voltage). For the some gaps we expect to reach the barrel limit (0. 05 C/cm 2) end of the year.

RB 1 Rate by cluster counting in the aging position Comparison between different “aging” test periods @ ABS 1 May Forward January Backward

Currents: an increase of ohmic current until March was related to the low gas flow rate during the first months of operation. We observed that can be cured by increasing the gas flow rate and flowing pure argon through the chambers. Chamber 26 Source OFF Down gap Up gap Chamber 26 Source ON Down gap Up gap

Efficiency during aging period: 3 small RPCs used for trigger during the efficiency runs (cosmic trigger with source OFF). Logic AND of ORed signals from each chamber: 40 cm x 40 cm Efficiency check started in February.

We will test the efficiency during all summer period with the muon beam. Efficiency with muon beam at different rates Efficiency (%) Test position A Comparisons between 2 “beam test” periods ( May – June) Test position A Beam on forward 26 and backward 25

Test position B Beam on the forward side for chamber 25 and backward for chamber 26. Efficiency: comparison between single and double gaps double up down Efficiency (%) double up

Test position B Beam on the forward side for chamber 25 and backward for chamber 26. Rate (Hz/cm 2) Rate: Comparisons between single and double gaps

Currents with beam on @ different ABS

Future • Next week we will connect the chambers to the close loop gas system • We will continue the data taking with the muon beam at different ABS and different positions • In august we have to move the chambers out of the area • In September 2 additional weeks of muon beam • Hope to finish the test at the end of the year.