Spin physics at Storage Rings April 11, 2015 Frank Rathmann Barschall/Haeberli Symposium, Madison

My first contact with Willy Erhard Steffens me Willy I first met Willy on the occasion of the 1991 workshop on üpolarized gas targets at Heidelberg. Kisten Zapfe  Workshop on Polarized Gas Targets, Heidelberg, Fall 1991 f.rathmann@fz-juelich.de Spin Physics at Storage Rings

1992: The first 𝑝𝑝 spin filtering experiment at HD Goal: Produce a beam of polarized antiprotons The apparatus was there, and the target and polarimeter TSR Before Willy came, it was clear to everyone (students and professors alike) that we would measure the target polarization using 𝑝𝑝 elastic scattering. Within a day after Willy had inspected the equipment and the anticipated measurements, it became clear that this would simply not work! The analyzing power of 𝛼𝑝 scattering ( 𝐴 000𝑛 =−0.843) exceeds the one of pp scattering by about a factor 100, so we did dedicated runs with stored 𝛼 particles to determine the target polarization. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

1992: Preparation of the storage cells improvized spot welding FEP 120 0.2 mm Al 𝑷=𝟎.𝟐𝟖±𝟎.𝟎𝟏 FEP 120 0.2 mm Al 𝑷=𝟎.𝟑𝟓±𝟎.𝟎𝟏 TPFE 3170 0.2 mm Al 𝑷=𝟎.𝟒𝟒±𝟎.𝟎𝟏 The openable cell had been developed because accelerator physicists were cautions about obstructions. But this cell showed a much smaller target polarization than expected. Eventually the machine people learned how to inject and cool the beam in the presence of a closed cell. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

2011: Spin filtering at COSY In 2009, the PAX collaboration submitted a proposal for spin filtering studies using antiprotons at the AD, and the SPSC of CERN requested another spin filtering experiment with protons. Measured spin-dependent cross section fully consistent with NN scattering. W. Augustyniak et al., Phys. Lett. B 718 (2012) F. Rathmann et al., Phys.Rev.Lett. 71 (1993) After the results were published, the SPSC concluded that spin filtering experiments would not fit into the present AD program. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

Spin Physics at Storage Rings 1994: Move to Madison After my PhD in January 1994, Willy offered me a PostDoc position at UW. In May 1994, I came to Madison on a Fellowship of the Alexander von Humboldt Foundation. In July 1994, my wife Andrea, 2 year Isabel and ¾ year Leonard followed. Willy and Gabi greatly supported us in all relevant aspects. Our years in Madison (1994 – 1997) were just fantastic. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

1994-2003: Experiments at the Indiana Cooler 𝒑𝒑 elastic scattering: Almost free of background, complete angular distributions, spin correlations 𝐴 𝑥𝑥 , 𝐴 𝑦𝑦 , 𝐴 𝑥𝑧 , and 𝐴 𝑦 , lateron we also measured 𝐴 𝑧𝑧 using longitudinal beam polarization. Very small normalization uncertainties, and very small statistical errors. This was real fun! How long does it take to reverse the target polarization? 𝜏=7±1 ms W. Haeberli et al., Phys. Rev. C 55 (1997) F. Rathmann et al., Phys. Rev. C 58 (1998) B. von Przewoski et al., Phys. Rev. C 58 (1998) B. Lorentz et al., Phys. Rev. C 61 (2000) f.rathmann@fz-juelich.de Spin Physics at Storage Rings

1994-2003: Experiments at the Indiana Cooler Nuclear polarization of Hydrogen Molecules: Experiment used a storage ring to measure the nuclear polarization of molecules formed by recombination of Hydrogen atoms in a cell. entrance tube 200 MeV proton beam Teflon coated target cell Teflon valve Copper recombiner superconducting current loop atomic beam T. Wise et al., Phys. Rev. Lett. 87 (2001). Faction of proton polarization retained in molecules f.rathmann@fz-juelich.de Spin Physics at Storage Rings

Spin Physics at Storage Rings 2000 - present: Jülich Nuclear polarization of Hydrogen Molecules: Since then, these studies were continued in Jülich. A new device was built making this possible without an accelerator. Glas cell cover by a gold surface Additional covering by Teflon, Fomblin, etc. Crucial: Can be heated to 400 C superconducting solenoid This effort started after a continental breakfast with Willy at the Hampton Inn in Bloomington, IN (~1999) during a run at the Indiana Cooler. Back in Jülich we started to develop the device, together with our colleagues from Gatchina, Russia. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

2000 - present: Jülich Nuclear polarization of Hydrogen Molecules: The Jülich polarized ABS was used during time periods, when we are not running the storage ring experiments Installation at the ANKE magnet spectrometer spectrometer at COSY Off beam installation The polarized ABS on its way into the internal target station. Device was designed to do that within a maintenance week. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

Spin Physics at Storage Rings 2000 - present: Jülich Nuclear polarization of Hydrogen Molecules: Recent progress preliminary T=100 K Because of the superconducting solenoid, there is very little water in the vaccum vessel. The results shown here are achieved with a clean surface during one day. f.rathmann@fz-juelich.de Spin Physics at Storage Rings

Willy, I always enjoy working with you. I wish you all the best Frank Valerie, one of the Wisonsin souvenirs we took back to Germany. Willy, I always enjoy working with you. I wish you all the best Frank f.rathmann@fz-juelich.de Spin Physics at Storage Rings