Cryogenic R5912-20Mod photomultiplier tube characterization for the ProtoDUNE dual phase detector

Abstract

A: The Deep Underground Neutrino Experiment (DUNE) is a dual-site experiment for longbaseline neutrino oscillation studies, and for neutrino astrophysics and nucleon decay searches. The far detector is a 40-kton underground liquid argon time-projection-chamber (LAr TPC), in which the photon detector system adds precise timing capabilities. The ProtoDUNE Dual-Phase detector will consist of a 6×6×6 m 3 LAr TPC to be operated at the CERN Neutrino Platform and the photon detection system will be formed by 8-inch cryogenic photomultipliers from Hamamatsu. The PMT model (R5912-20Mod) performance at cryogenic temperature is studied including dark current, gain, and linearity with the light intensity and pulse rate. In addition, the PMT base design is validated. At cold, a decrease of the PMT amplification, or fatigue effect, is measured as the PMT output current increases, either, due to high gain, light intensity or rate. Also, the characterization results of the 40 photomultipliers to be used in ProtoDUNE Dual-Phase are presented. K: Noble liquid detectors (double-phase); photon detectors (photomultipliers); neutrino detectors;

Status of ProtoDUNE Dual Phase

“…The photon detection system of ProtoDUNE-DP [6] is formed by 36 8-inch cryogenic PMTs (R5912-02MOD from Hamamatsu) placed below the cathode grid. The ProtoDUNE-DP PMTs were validated and characterized [7] . As wavelength shifter, a sheet of polyethylene naphthalate (PEN) is placed on top of 30 PMTs and the other 6 PMTs have tetraphenyl butadiene (TPB) directly coated on them.…”

A light calibration system for the ProtoDUNE-DP detector

“…The LCS must illuminate 36 PMTs at Single Photo-Electron (SPE) level and at larger light intensities to ensure that the gain calibration and the linearity can be determined from the data. The acquisition rate is not a strong requirement since the rate should be kept within ∼kHz to avoid the PMT fatigue [10].…”

“…The estimated light attenuation of the total system is compared with the attenuation from dedicated PMT measurements at CT. The setup characterization [10] is used for this test. The measurements are performed simultaneously with 5 R5912-02MOD Hamamatsu PMTs placed inside a 300 l vessel filled with LN 2 at 77 K. The LED is used as an external light source and the amount of light is configurable varying the voltage.…”

“…As wavelengthshifter, tetraphenyl butadiene (TPB) is coated directly on the PMTs. The ProtoDUNE-DP PMTs have been validated and characterized [10].…”

Scintillation light production, propagation and detection in the 4-ton dual-phase LAr-TPC demonstrator (data analysis and simulations)

“…It showed the possibility to extract the drifted electrons over a 3 m 2 surface, to multiply them using 50x50 cm 2 LEM units and to read them out on two collection planes with strips with a maximum length of 3 m. The light detection system demonstrated it can provide the t 0 time for the charge DAQ, so that it could be used as self trigger for the cosmic muons. To accomplish these requirements and to obtain complementary calorimetric information from the scintillation and electro-luminescence light signals, the light detection system used five eight inches cryogenic R5912-02Mod PMTs [3] positioned underneath the cathode. To find the optimal configuration to be implemented in the DUNE DP FD module, the light detection system tested different PMT configurations in terms of base polarity (positive and negative bases) and wavelength shifter.…”