Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 49 (2016)

Commissioning of SCRIT electron scattering facility with stable
nuclear targets
K. Tsukada,∗1,∗2 K. Adachi,∗1,∗3 A. Enokizono,∗1,∗3 T. Fujita,∗1,∗3 M. Hori,∗1,∗3 K. Kurita,∗1,∗3 T. Ohnishi,∗1T. Suda,∗1,∗2 T. Tamae,∗1,∗2 K. Yamada,∗1,∗3 M. Wakasugi,∗1 and M. Watanabe∗1clearly seen. Figure 3 shows the angular distribution ofelastic events corrected by the acceptance after background subtraction. In the present analysis, it is assumed that the xenon ions are distributed uniformly in
the SCRIT. In the forward region, the calculation andour results are almost consistent. The statistics, however, is not enough in the backward region to discuss
the consistencies. Even now, the data taking are being
continuously taken by using the 132 Xe target with anelectron energy of 150 MeV.
In summary, the angular distributions of a stable nuclear target have been measured and compared with aDWBA calculation. Before proceeding to experimentswith unstable nuclei, we need more studies with stabletargets to understand the acceptance.
150IonIN
40msecIonOUTIon
IN

Target Ion IN

40msec10msecTarget Ion OUT

100500-300-200-1000100

200300Z [mm]

Fig. 2. Vertex point distribution along the beam line. Innerﬁgure shows the time structure of the target conditions.

10 2L dσ [(cm -2s-1)(cm 2sr -1)]dΩThe SCRIT electron scattering facility has been developed at RIBF for realizing electron scattering oﬀ
unstable nuclei. Construction of a magnetic spectrometer, WiSES (Window-frame Spectrometer for Electron Scattering), and a luminosity monitor almost ﬁnished in November 2014, and the detector commissioning started1,2) . ERIS (electron-beam-driven RI separator for SCRIT) and an ion transportation system havebeen continuously developed up until now to increase
the target ion trapped in the SCRIT.
This year, commissioning experiments with several
kinds of stable nuclear targets have been performed inorder to evaluate the performance of SCRIT facility.
Metal wires of diameter 50 μm made of tungsten
and titanium were horizontally mounted at the center of the SCRIT device as stable nuclear targets. Bychanging the position of these wires remotely, the luminosity can be controlled. Figure 1 shows the angular distribution of elastic scattering events correctedby the acceptance for the tungsten target. These data
were taken in July 2015. Although a DWBA calculation3) is consistent with our results in the forward
region, there are small discrepancies of around 50◦ .
The xenon ion beams have been stably provided byERIS4) . For the commissioning, 132 Xe was used as astable target because the natural abundance of 132 Xe
is 26.9%, which is the largest in the series of xenon
isotopes. Figure 2 shows the vertex point distribution
along the beam line. These data were taken in December 2015. As shown in the inner ﬁgure of Fig. 2, theconditions of 132 Xe and the empty target interchanged
every 50 ms with an interval of 10 ms.
The diﬀerence between Ion IN and Ion OUT is

Ee=150 MeV
Exp. Ion IN-OUT
132
DWBA calc., for Xe
assuming L=2.2x1026 [cm-2 s-1 ]10preliminary

1

L dσ [(cm -2s-1)(cm 2sr -1)]
dΩ

10 -1

Ee=200 MeV
Exp. data
184
DWBA calc. for W
assuming L=2.1x1028 [cm -2s -1 ]10 310 210 -225

preliminary

1405060
Scattering angle [deg]Fig. 1. Obtained diﬀerential cross section for tungsten target at the electron beam energy of 200 MeV. The solidline is a calculation by DWBA code assuming averaged
luminosity of 2.1×1028 [cm−2 s−1 ].
∗1∗2∗3354045505560
Scattering Angle [deg]Fig. 3. Obtained diﬀerential cross section for 132 Xe target
at the electron beam energy of 150 MeV. The solid line
is a calculation by DWBA code assuming averaged luminosity of 2.2×1026 [cm−2 s−1 ].

103030RIKEN Nishina Center
ELPH, Tohoku University
Department of Physics, Rikkyo University- 187 -References
1) K. Tsukada et al., Accel. Prog. Rep. 48, 23 (2015).
2) S. Yoneyama et al., Accel. Prog. Rep. 48, 227 (2015).
3) B. Drepher et al., a phase-shift calculation code for elastic electron scattering, communicated by J. Friedrich.
4) T. Ohnishi et al., in this progress report.