Analyzing powers for→1(π+

Abstract

We have measured the analyzing power for elastic scattering of ϩ from a target of polarized 1 H. Data were taken for incident pion beam energies of 165 and 240 MeV at several pion scattering angles. The current data generally agree with previously existing measurements of A y for this reaction and also with results of the SAID phase-shift analysis program. In most cases the new data are of higher precision than previously existing data.PACS number͑s͒: 13.75. Gx, 24.70.ϩs, 25.80Dj We have measured the analyzing powers for elastic scattering of ϩ from polarized 1 H for pion beam energies of T ϭ165 and 240 MeV at several scattering angles. Previously reported results for beam energies near 165 MeV ͓1-3͔ do not extend to the small angles accessible to this experiment while previous results near 240 MeV ͓4,5͔ have relatively large uncertainties. The data presented here were acquired during two separate running periods at the Paul Scherrer Institute ͑PSI͒ in Villigen, Switzerland with very similar experimental setups. The main thrust of the first running period was to measure the analyzing power for the 7 Li ជ ( ϩ , ϩ p) reaction at T ϭ240 MeV ͓6͔ while the second running period focused on measuring the 7 Li ជ ( ϩ ,pp) analyzing power at T ϭ165 MeV ͓7͔. Both experiments utilized a polarized 7 LiH target. The presence of polarized hy-drogen in this target allowed us to gather 1 H ជ ( ϩ , ϩ p) analyzing power data along with the primary 7 Liϩ ϩ data. Initially, the 1 H ជ ( ϩ , ϩ p) data were analyzed to monitor stability of the target polarization. The high quality and internal consistency of these data prompted the writing of this Brief Report.Central to the success of the 7 Li experiments was the development of the PSI polarized 7 LiH target ͓8͔. The target consisted of chips of irradiated 7 LiH contained in an 18 mm wide by 18 mm high by 5 mm thick brass cavity. NMR coils were located in the median plane of the cavity to provide periodic monitoring of the target polarization. The cavity is held in the mixing chamber of a dilution refrigerator at the center of a 2.5 T magnetic field. The target was dynamically polarized yielding a positive polarization ͑normal to the scattering plane in the direction of the magnetic field͒ of hydrogen nuclei between 45 and 60 % and negative polarization between 40 and 50 %. The target polarization was determined to within an accuracy of Ϯ4% of the measured polarization value using the PSI NMR system ͓9͔. During the 240 MeV running period, a single NMR coil measured the polarization of the 7 Li and the 1 H polarization was deduced using the equal spin temperature theory. For the 165 MeV running period, a second NMR coil provided a direct measurement of the 1 H polarization in addition to the direct measurement of the 7 Li polarization. The measured 1 H polarization and that deduced from the equal spin temperature theory, using the measured 7 Li polarization, are consistent within the uncertainties ͓7͔. In addition to 7 Li and 1 H, the target also contained liquid 4 He and a small amo...

Fast neutron detection with a segmented spectrometer

“…This optical decoupling prevents crosstalk between the segments. The segments were repurposed from another experiment [50], and no structural changes were made to them. The 3 He proportional counters were manufactured by Reuter Stokes and have a 2.54 cm diameter aluminum body and an active length of 46 cm.…”

“…This optical decoupling prevents crosstalk between the segments. The segments were repurposed from another experiment [50], and no structural changes were made to them.…”