Measurement of scintillation and ionization yield with high-pressure gaseous mixtures of Xe and TMA for improved neutrinoless double beta decay and dark matter searches

摘要

The gaseous Xenon(Xe) time projection chamber (TPC) is an attractive detectortechnique for neutrinoless double beta decay and WIMP dark matter searches.While it is less dense compared to Liquid Xe detectors, it has intrinsicadvantages in tracking capability and better energy resolution. The performanceof gaseous Xe can be further improved by molecular additives such astrimethylamine(TMA), which is expected to (1) cool down the ionizationelectrons, (2) convert Xe excitation energy to TMA ionizations through Penningtransfer, and (3) produce scintillation and electroluminescence light in a moreeasily detectable wavelength (300 nm). In order to test the feasibility of theperformance improvements with TMA, we made the first direct measurement ofPenning and fluorescence transfer efficiency with gaseous mixtures of Xe andTMA. While we observed a Penning transfer efficiency up to ~35%, we foundstrong suppression of primary scintillation light with TMA. We also found thatthe primary scintillation light with Xe and TMA mixture can be wellcharacterized by ~3% fluorescence transfer from Xe to TMA, with furthersuppression due to TMA self-quenching. No evidence of the scintillation lightproduced by recombination of TMA ions was found. This strong suppression ofscintillation light makes dark matter searches quite challenging, while thepossibility of improved neutrinoless double beta decay searches remains open.This work has been carried out within the context of the NEXT collaboration.