The large COMPASS polarized solid ammonia target for Drell-Yan measurements with a pion beam

0556655 - ÚPT 2023 RIV NL eng J - Journal Article
Andrieux, A. - Berlin, A. - Doshita, N. - Finger, M. - Finger jr., M. - Gautheron, F. - Horikawa, N. - Ishimoto, S. - Iwata, T. - Kisselev, Y. - Koivuniemi, J. H. - Kondo, K. - Magnon, A. - Mallot, G. K. - Matoušek, J. - Matsuda, T. - Meyer, W. - Miyachi, Y. - Nukazuka, G. - Pešek, M. - Pires, C. - Quintans, C. - Reicherz, G. - Runkel, S. - Srnka, Aleš - Suzuki, H.
The large COMPASS polarized solid ammonia target for Drell-Yan measurements with a pion beam.
Nuclear Instruments & Methods in Physics Research Section A. Roč. 1025, 11 February (2022), č. článku 166069. ISSN 0168-9002. E-ISSN 1872-9576
Research Infrastructure: CERN-CZ - 90058; CERN-CZ II - 90104
Institutional support: RVO:68081731
Keywords : Polarized solid target * Drell-Yan * COMPASS * DNP * Ammonia target * NMR
OECD category: Particles and field physics
Impact factor: 1.4, year: 2022
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S0168900221009918

The transversely polarized target (PT) of the COMPASS (NA58) collaboration at CERN has been used for Drell-Yan measurements in 2015 and 2018. The transverse spin structure of the proton has been studied using a negative pion beam and a solid ammonia target. Employing the dynamic nuclear polarization (DNP) method, proton polarization values of more than 80% have been routinely achieved after one day, at a homogeneous magnetic field of 2.5 T and using a He-3/He-4 dilution refrigerator. During the data-taking the target operates in a transversely oriented magnetic dipole field at 0.6 T. This so-called frozen spin operation mode without the DNP pumping process leads to a slow depolarization of the target material, which is further accelerated by the heat input of the pion beam, produced secondary particles and radiation damage effects to the target material. Ammonia has the highest resistance against radiation-induced depolarization among known solid target materials. The proton polarization has been measured by the nuclear magnetic resonance (NMR). Relaxation times of about 1100 h have been observed for the proton polarization resulting in an average polarization between 68% and 76% during about two weeks long data-taking periods. To achieve a systematic uncertainty of the polarization Delta P/P as low as 3.2% and a statistical one of less than 1.8% two large target cells with appropriate positioning of the NMR-coils have been built.
Permanent Link: https://hdl.handle.net/11104/0333696