14-17 September 2021
America/Los_Angeles timezone

Development and characterization of a slow wavelength shifting coating for background rejection in liquid argon detectors

17 Sep 2021, 12:00
Detector techniques (HV, purification, cryogenics, calibration etc.) Detector Techniques (4B)


David Gallacher (Carleton University)


Alpha decays occurring on surfaces of a liquid argon (LAr) detector, particularly in locations where light collection is incomplete, can result in prompt apparent low-energy events that reconstruct similar to dark-matter induced nuclear recoil events. Alphas and nuclear recoils preferentially excite argon into the singlet state, which decays with a characteristic time of ~6 ns. To convert the argon scintillation light to visible, a wavelength shifter, TPB, is typically used due to its short (O(ns)) re-emission time, that will preserve the LAr scintillation timing. By coating the problematic detector surface with a wavelength shifting coating with a decay time constant much longer than the LAr singlet time, the pulse-shape of alpha decays from these regions will be modified by the coating, with O(10^5) rejection efficiency expected. We describe the development of a pyrene-doped polymeric wavelength shifting film for the DEAP-3600 experiment, which will be deployed in the next major physics run after the completion of a suite of hardware upgrades to the detector. We will present an overview of the alpha background rejection technique using the long-time constant wavelength shifter coating, the development and testing of the films to ensure cryogenic stability for operation in a LAr environment, and the suite of characterization measurements of the film’s critical operational parameters, including relative photo-luminescent quantum yield, emission spectrum, and characteristic decay time

Primary author

David Gallacher (Carleton University)


Dr Marcin Kuźniak (AstroCeNT / CAMK PAN)

Presentation Materials