The compact muon solenoid hadronic forward calorimeter photomultiplier tube tests during the first long shutdown

CERN, the European Organization for Nuclear Research, is an international scientific collaboration founded at 1954 near Geneva. The machines at CERN are particle accelerators and detectors. CERN complex accelerator includes many experiments apart from the LHC experiment. The LHC experiment analyses the particles at the collisions by using its detectors. They are namely ALICE, ATLAS, CMS and LHCb. ATLAS and CMS are general-purpose detectors. ALICE searchs for the structure of quark-gluon plasma which is a phase of matter just after the Big Bang. LHCb investigates the difference between matter and antimatter by using b quarks. The CMS detector is as a cylindrical shape detector and consists of ECAL, HCAL, Muon Stations and Tracking subdetectors. The CMS detector has many physical research programme from Standart Model to extra dimensions and dark matter. The HCAL analyses hadrons and also indirectly uncharged particles, neutrinos. In addition to these goals of the HCAL with ECAL, it searchs for electron/photon, muon and tau identities. The HCAL consists of four sections, barrels ones, HO and HB, endcap HE, and forward HF. The HCAL has two hadronic forward calorimeters, namely HF+ and HF-, the either side of the CMS detector. The HF was made of iron absorber as a passive medium and quartz fiber optics cable as an active medium. Totally, it consists of 36 wedges. Each wedge has two readout boxes and each readout box has 24 PMTs. Totaly, the HF calorimeter has 1728 PMTs. Before the phase 1 of LS1, photomultiplier tubes constructed on the HF are Hamamatsu R7525 PMTs. The purpose of these new Hamamatsu R7600U-M4-200 PMTs with four anodes changing with the old PMTs is to reduce the rate of the anomalous signals from background events. In order to bear this faulty, these new PMTs with higher gain, quantum efficiency and thinner window were chosen to replace with the old PMTs assembled on the HF calorimeter. Also, PMT's baseboard were tested at this station. During phase 1 of LS1, these new PMTs were tested in the PMT and baseboard test station at B904 building at CERN. There are two darkboxes instead of roboxes constructed on the HF calorimeter. Each darkbox has 24 PMTs. At the station, the primary goal is to sort the new PMTs as low, middle and high gain to be assembled on the HF calorimeter. These tests were perfomed by using the blue light emitting diode. This light was used in two types as LED and SPE having different intensities from each other. Some characteristic properties of these new PMTs were analyzed with statistical calculations with respect to PMT test data taken at LED and SPE intensity at the station.