An innovative technique for TPB deposition on convex window photomultiplier tubes

Abstract

A: Tetraphenyl-butadiene (TPB) is an organic fluorescent chemical compound generally used as wavelength shifter thanks to its extremely high efficiency to convert ultra-violet photons into visible light. A common method to use TPB with detectors sensitive to visible light, such as photomultiplier tubes (PMTs), is to deposit thin layers on the device window. To obtain effective TPB layers, different procedures can be used. In this work a specific evaporation technique adopted to coat 8 in convex windows photomultiplier tubes is presented. It consists in evaporating TPB by means of a Knudsen cell, which allows to strictly control the process, and in a rotating sample support, which guarantees the uniformity of the deposition. Simulation results and experimental tests demonstrate the effectiveness of this evaporation technique from the point of view of deposition uniformity and light conversion efficiency. K : Photon detectors for UV (photomultipliers); Noble liquid detectors; Monochromators. 1Corresponding author. Now at Brookhaven National Laboratory, Brookhaven NY, USA. arXiv:1807.07123v4 [physics.ins-det]

Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC

“…While TPB is broadly used, PEN is a novel material, never used before in such a large scale experiment and whose efficiency is not well known. As TPB needs complex coating setups [ 25 ], the potential benefit of PEN comes from its simple handling, because PEN foils are flexible plastic sheets easy to fabricate and install. The PEN sample used in ProtoDUNE-DP is transparent and biaxially oriented, manufactured by GoodFellow [ 26 ].…”

“…2 . TPB was deposited over the PMT polished surface, using a dedicated evaporation system developed by the ICARUS experiment [ 25 ]. The coating density is 0.2 mg/cm , which corresponds to a coating thickness around 0.2 m. Both PEN and TPB have a maximum of re-emitted photons around a wavelength of 430 nm [ 27 , 28 ].…”

Scintillation light detection in the 6-m drift length ProtoDUNE Dual Phase liquid argon TPC

“…2. TPB was deposited over the PMT polished surface, using a dedicated evaporation system developed by the ICARUS experiment [25]. The coating density is 0.2 mg/cm 2 , which corresponds to a coating thickness around 0.2 m. Both PEN and TPB have a maximum of re-emitted photons around a wavelength of 430 nm [27,28].…”

Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC

“…2. TPB was deposited over the PMT polished surface, using a dedicated evaporation system developed by the ICARUS experiment [25]. The coating density is 0.2 mg/cm 2 , which corresponds to a coating thickness around 0.2 µm.…”