time spread of 180 ps, a time resolution of about 30 ps is needed. Since the expected pile-up is around 200, with an r.m.s. The upgrades of ATLAS and CMS for the High Luminosity LHC (HL-LHC) highlighted physics objects timing as a tool to resolve primary interactions within a bunch crossing. Furthermore I acknowledge the support of the PHENIICS Doctoral school program, Université Paris-Saclay, and the financial support of the Cross-Disciplinary Program on Instrumentation and Detection of CEA, the French Alternative Energies and Atomic Energy I acknowledge the support of the CERN Summer Student Program and the CERN EP-DT-DD-GDD lab during my stays for the beam measurements at CERN in 2017. I acknowledge the support of the RD51 collaboration, in the framework of RD51 common projects. The lack of photo electrons affect the time resolution in this parts and the outer areas are not suitable as a t 0-reference. In the outer parts only partial and/or reflected light reaches the photocathode. Nevertheless the necessary performances are only archived in the inner parts of the MCP-PMT up to an radius of 5.5 mm. With this work the usability of MCP-PMTs as a t 0-reference detector for DUTs with an expected time resolution >10 ps is shown.
![photoshop 5.5 light beams photoshop 5.5 light beams](https://i.ytimg.com/vi/V2PSEMApvPY/maxresdefault.jpg)
The standard deviation of this distribution represents the total time resolution of this measurement. The time difference follows a Gaussian distribution. In this case the t 0-reference is equal to the DUT therefore two identical MCP-PMTs are used and the time difference between both signals is calculated. The time resolution is in general calculated by the time difference between the DUT and a t 0-reference detector. The main study of this work is the spatial dependence of the time resolution. The distribution of this ratio along the radius of the MCP-PMT is shown in Fig. 2. Tracking data allow to measure the MCP-PMT efficiency as a function of impact position by calculating the ratio between the number of tracks hitting the MCP-PMTs active area and producing a signal and the total number of tracks hitting the same area. The EfficiencyĪ most important feature of a reference detector is its detection efficiency which should be as high and uniform as possible over the active area.
#PHOTOSHOP 5.5 LIGHT BEAMS FULL#
The full waveforms are sampled and a pulse shape analysis has been performed off-line. The MCP-PMTs and DUTs are read out with sampling Oscilloscopes. It additionally hosts two MCP-PMTs as time reference devices and up to three mounting positions for various DUTs. This beam telescope consists of triple-GEM detectors as tracking devices and scintillators with a coincidental PMT read-out as trigger devices. Measurements have been performed with a beam telescope in a muon beam at CERN/SPS-H4. This explains the strong spatial differences of the MCP-PMTs time resolution. The pulse amplitude correlates with the number of generated photo electrons and therefore with the amount of light reaching the photocathode.
![photoshop 5.5 light beams photoshop 5.5 light beams](https://i.ytimg.com/vi/os-qqVrMc-Q/maxresdefault.jpg)
Finally, only diffuse reflected light is reaching the photocathode in the outermost parts. In this region, the Cherenkov light cone is not fully projected onto the photocathode anymore. In the outer parts, the time resolution declines up to several ten picoseconds due to decreasing pulse amplitudes. A time resolution of up to 3.8 ps has been obtained in the inner part of the active area. These measurements were conducted during the tests of PICOSEC fast-timing Micromegas prototypes at the CERN/SPS-H4 beam line using a beam telescope consisting of three triple-GEM tracker and various trigger detectors. Measurements with MCP-PMTs of the type R3809U-50 by Hamamatsu have been performed in order to characterise their spatial distribution of the time resolution and to validate them as a proper reference detector. The time resolution of the reference detector, normally placed together with a device under test (DUT) in a beam telescope, should be considerably better than the time resolution of the DUT. A hyper-fast time reference is needed for characterisation measurements of fast-timing detector prototype.