Beam Diagnostics for Measurements of Antiproton Annihilation Cross Sections at Ultra-low Energy

K Todoroki,V Mascagna,N Zurlo,T Kobayashi,M Leali,R Hayano,E Vallazza,M Hori,M Prest,A Soter,L Venturelli,E Lodi-Rizzini,D Barna,M Corradini,H Aghai-Khozani

doi:10.1051/epjconf/20146609020

Abstract

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antipro- tons) collaboration of CERN is currently attempting to measure the antiproton-nucleus in-flight annihilation cross sections on thin target foils of C, Pd, and Pt at 130 keV of kinetic energy. The low-energy antiprotons were supplied by the Antiproton Decelera- tor (AD) and a radio-frequency quadrupole decelerator. For this measurement, a beam profile monitor based on secondary electron emission was developed. Data from this monitor was used to ensure that antiprotons were precisely tuned to the position of an 80- mm-diameter experimental target, by measuring the spatial profile of 200-ns-long beam pulses containing 10 5 10 6 antiprotons with an active area of 40 mm 40 mm and a spa- tial resolution of 4 mm. By using this monitor, we succeeded in finely tuning antiproton beams on the target, and observed some annihilation events originating from the target.

Highlights

Several groups have previously measured the cross sections of in-flight antiprotons annihilating on targets of various mass numbers at kinetic energies E > 600 keV, by using the Low Energy Antiproton Ring (LEAR) at CERN [1,2,3,4,5,6]
The 5.3-MeV antiprotons provided by the Antiproton Decelerator (AD) of CERN was allowed to pass through a radiofrequency quadrupole decelerator (RFQD), which reduced the kinetic energy of 30 % of the antiprotons to 130 keV
Despite the simplicity and low cost of this monitor, it had adequate sensitivity to measure the profiles of beams containing ∼104 antiprotons

Summary

Introduction

Several groups have previously measured the cross sections of in-flight antiprotons annihilating on targets of various mass numbers at kinetic energies E > 600 keV, by using the Low Energy Antiproton Ring (LEAR) at CERN [1,2,3,4,5,6]. The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration of CERN measured the antiproton-nucleus annihilation cross sections with targets of Mylar, Ni, Sn, and Pt at E = 5.3 MeV [7, 8] These experimental results were consistent with the prediction of a modified black-disk model, which implies that the antiproton is strongly absorbed near the nuclear surface, and that the real potential is weaker compared to the imaginary one [9]. In this experiment, the 5.3-MeV antiprotons provided by the Antiproton Decelerator (AD) of CERN was allowed to pass through a radiofrequency quadrupole decelerator (RFQD), which reduced the kinetic energy of 30 % of the antiprotons to 130 keV. This monitor was a secondary electron emission detector with an active area of 40 mm × 40 mm and a spatial resolution of 4 mm

Beam Profile Monitor

Findings

Conclusion