Mitglied der HelmholtzGemeinschaft Dipole Magnetic Field Effect on

Mitglied der Helmholtz-Gemeinschaft Dipole Magnetic Field Effect on the Antiproton Beam June 15 th, 2009 | T. Randriamalala, J. Ritman and T. Stockmanns

The Why of the Topic Where should the luminosity monitor be located when the dipole field is on? How does the B field act on the trajectory of the antiproton beam? The beam pipe bend should match the curvature of the antiproton trajectory so that antiproton scattered with q < 8 mrad do not hit the beam pipe. 25 December 2021 Folie 2

Luminosity Monitor Position For the dipole: Trajectory curvature radius inside the dipole region: The angle between the z-axis direction and the antiproton beam trajectory after the bend is 40 mrad. The dipole is located at about z = 4. 5 m At z =10 m, the luminosity monitor is at x ~ 21 cm 25 December 2021 Folie 3

According to the Magnets TDR: Antiproton beam trajectories corresponding to the momentum of 1. 5 Ge. V/c to 15 Ge. V/c. The leftmost line is for a 15 Ge. V/c beam, the rightmost line is for a 3 Ge. V/c beam. 400 mm The maximum distance between these trajectories at z = 10 m is about 0. 4 mm. 25 December 2021 Folie 4

Working with pandaroot: At z = 10 m, the luminosity monitor was shifted at x = 21 cm and rotated with an angle of 40 mrad. Run the simulation macro for the luminosity monitor for different values of beam momentum. ! With some of these values, no hits are observed. 25 December 2021 Folie 5

The Dipole Field Maps in Panda. Root Test of the dipole field maps by running a simple simulation: Put one active plane at z =10 m. No detector, or beam pipe. Switch all the magnetic field on: solenoid , dipole, transition region. Run for different values of beam momentum (1. 5 Ge. V/c, 4. 6 Ge. V/c, 8. 9 Ge. V/c, 11. 91 Ge. V/c and 15 Ge. V/c). 25 December 2021 Folie 6

Hit x-position for 5000 events Only hits corresponding to 1. 5 Ge. V/c and 15 Ge. V/c sit at the right position. ~ 325 mm Agree with the Magnets TDR (~ 370 mm) 25 December 2021 Folie 7

The corresponding intensity of magnetic fields for 4. 06 Ge. V/c and 11. 91 Ge. V/c are not “strong” enough to redirect beam in the correct position. In contrast, for 8. 9 Ge. V/c, the magnetic field intensity is too high. 25 December 2021 Folie 8

In the Magnet TDR: [Tesla] Field distribution along the z-axis for different dipole settings for a 1. 5 Ge. V/c (solid black line and left scale) and a 15 Ge. V/c beam (dashed blue line and right scale). Re gi o le Z [cm] So le 15 Ge. V/c 1. 5 Ge. V/c po no By(z) [Tesla] id Re gi on Bz(z) [Tesla] n 1. 5 Ge. V/c Di y(z) Different dipole field maps implemented in pandaroot: Bz(z) [Tesla] 15 Ge. V/c Same shape and same scale ! Z [cm] 25 December 2021 Folie 9

8. 9 Ge. V/c By(z) [Tesla] Abrupt increase of the magnetic field intensity Bz(z) [Tesla] Z [cm] Antiprotons are bent too much! 25 December 2021 Folie 10

By(z) [Tesla] 4. 06 Ge. V/c Presence of cut Bz(z) [Tesla] 4. 06 Ge. V/c Z [cm] By(z) [Tesla] Antiprotons are not bent enough ! 11. 91 Ge. V/c Bz(z) [Tesla] 11. 91 Ge. V/c Z [cm] 25 December 2021 Folie 11

Conclusion Magnetic field maps inside pandaroot were tested. It does not work as well as what is described in the Magnets TDR. In particular those ones corresponding to the beam momentum 4. 6 Ge. V/c, 8. 9 Ge. V/c and 11. 91 Ge. V/c. This was already reported to the forum. 25 December 2021 Folie 12