Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 49 (2016)

Development of pepper-pot
pepper-pot emittance
Developmentemittancemonitor
monitorfor
forAVF
AVFcyclotron
cyclotron
Y. Kotaka,䠆1 Y. Ohshiro,䠆1 H. Yamaguchi,䠆1 N. Imai,䠆1 H. Muto,䠆4T. Nagatomo,䠆2 M. Kase,䠆2 K. Hatanaka,䠆3 and S. Shimoura䠆1In order to improve the injection efficiency from theHyper ECR ion source (Hyper ECRIS) to the Riken AVF
cyclotron, a pepper-pot emittance monitor1) has beendeveloped. The horizontal (x) and vertical (y) beam
elements are coupled in this injection beam line because
three solenoid coils and two Glaser coils exist.
Consequently, a four-dimensional distribution (x, x’, y, y’)of the beam is necessary for measurement. In this report, wepresent the performance of the pepper-pot emittancemonitor, which can measure four-dimensional distributions.

Fig. 1. Top view of Hyper ECRIS and the beam line
Figure 1 shows the test set to determine the performanceof the pepper-pot emittance monitor. The figure shows atop view of the beam line from the Hyper ECRIS toDMI23. DMI23 is a dipole magnet that bends the beam in
the vertical direction. On the straight line from theanalyzing magnet to DMI23, a beam profile monitor(PF_IH10), a pepper-pot emittance monitor, a solenoid
coil (SOIH11) and a viewer plate (I23viewer) exist in thisorder. PF_IH10 is used for the alignment of the pepper-potemittance monitor.
We irradiated the pepper-pot emittance monitor with a4He2+ 20 keV ion beam (51eμA). The beam image of thepepper-pot emittance monitor is shown in the left part ofFig. 2. Using this, the four-dimensional distribution is
calculated and indicated as the vector in the right part of Fig.
2.

Fig. 2. Distribution of beam vector measured by thepepper-pot emittance monitor
Center for Nuclear Study, University of Tokyo
RIKEN Nishina Center
䠆3RCNP, Osaka University
䠆4Center of General Education, Tokyo University of Science, Suwa
䠆1
䠆2Then, we transfer the four-dimensional distribution to theposition of the I23veiwer. The transfer matrix of SOIH11 isconstructed using the real solenoid model2). The result isshown as the image on the x-y plane in the left part of Fig. 3.
The right part of Fig. 3 shows the beam image of theI23viewer. Comparing the left and right images of Fig. 3,
we find that both shapes and positions are similar.

Fig. 3. The left image is the image obtained from thefour-dimensional distribution transferred to the position of
the I23viewer and the right image is a beam image on theI23viewer.
In order to obtain further confirmation, we also transfer
the four-dimensional distribution to the exit of DMI23 andthe result is shown as the image on the x-y plane in the leftpart of Fig. 4. For comparison, we place another pepper-pot
emittance monitor at the exit of DMI23 and measureanother four-dimensional distribution. This beam image isshown in the right part of Fig. 4. Both shapes and positions
are similar.

Fig. 4. The left image is the image obtained from thefour-dimensional distribution transferred to the exit of
DMI23 and the right image is the image obtained fromanother pepper-pot emittance monitor.
These results show that our pepper-pot emittance monitor
has the necessary performance to be useful for the analysisof the injection beam line. After this, we are going to design
the transport system of the injection beam line using thefour-dimensional distribution.
References

1) T.Hoffmann et al.: Proc. 9th BIW, Cambridge, USA, (2000),
p.432-439.
2) H. Wiedemann: Particle Accelerator Physics, 3rd ed. (Berlin,Springer, 2007)- 144 -