Ⅱ-9. Instrumentation
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Development of a new conﬁguration for the liquid hydrogen target
X. Wang,∗1 M. Kurata-Nishimura,∗2 H. Wang,∗3 T. Gao,∗2,∗4 K. Horikawa,∗5 H. Otsu,∗2 and K. Takahashi∗5This study reports the development of a new conﬁguration for the liquid hydrogen target, using a cryogenic proton and alpha target system (CRYPTA).1) We
study the complete kinematics of p(10 Be, pd ) reactionsat 230 MeV/nucleon. Recoil protons and deuterons exhibits a large scattering angular range (0◦ –70◦ ). To
cover these particles, we develop a new conﬁguration
for the liquid hydrogen target system located inside theCAesium iodide array for γ-ray Transitions in AtomicNuclei at high isospin Asymmetry (CATANA)2) frame.
Figure 1(a) shows the conceptional image of the new
conﬁguration and (b) shows the internal structure of thevacuum chamber. A 70-cc copper (Cu) buﬀer tank isconnected to the ﬁrst stage of a Giﬀord-McMohon cycle
refrigerator (ULVAC R20) using a 45-cm long Cu pipe.
A SUS O-ring is used to avoid leakage, and a small Curing is inserted to improve heat conductivity. The target cell is made of oxygen-free Cu and connected to thebuﬀer tank by two Cu tubes, which are used for inlet(green) and outlet (magenta), respectively. Havar foilwith a thickness of 6.5 µm was glued to the Cu window of the target cell and sandwiched by a Kapton ring.
Figure 1(c) shows the size of the target cell. The thickness of the target cell is 15 mm. The deformation of theHavar foil was measured to be 2 mm with a diﬀerenceof 1.2 atm. In the new conﬁguration, the target cell islocated at the downstream side of the vacuum chambernear the exit window (Fig. 1(b)). The chamber will beinserted into the CATANA frame. As a result, the cen-ter of the target is 25 cm more downstream than thecenter of the cryogenic head along the beam direction,
thus covering a solid angle of approximately 2π.
Temperature is monitored using two silicon diodethermometers (Scientiﬁc Instruments Si410AA). The
thermometers are labeled as “Sensor A” (SA) (placedbelow the heater) and “Sensor B” (SB) (placed at thebottom of the buﬀer tank) (Fig. 1(a)). Figure 2 shows
the variation in temperature and pressure with coolingtime in a cooling test. The target cell and buﬀer tank
was ﬁrstly pumped out at room temperature. It took lessthan 3 hours to cool SA from room temperature to 20 K,
whereas SB was at 25 K. Then the heater started to operate and SA was maintained at 20 K. SB was cooled
down to approximately 24 K with vacuum, and the system achieved dynamic equilibrium. Hydrogen gas wasﬁlled into the cell at 1650 hPa and liqueﬁed near the cold
head. Liquid hydrogen ﬂew down gradually and cooled
the system down to 21 K (Fig. 2(b)). Finally, the pressure was stabled at 1111 hPa, which is 33% lower thanthe pressure at which hydrogen gas was ﬁlled, indicating that the buﬀer tank and target cell was fully ﬁlled
by liquid hydrogen. It took approximately 1.5 hours tocompletely ﬁlled the buﬀer tank and target cell. In thenew conﬁguration, it takes 4.5 hours to cool down andfully ﬁll the system with liquid hydrogen.

Fig. 2. Variation in temperature and pressure with time ina cooling test: (a) overall variation; (b) zoom-in view ofthe hatch area illustrated in (a).

In summary, we have developed a new conﬁguration for the liquid hydrogen target system based on
CRYPTA. By implanting the buﬀer tank, the target cellis placed near the center of CATANA. The system will
be used ﬁrst in the SAMURAI-53 experiment. Moreover, such a new conﬁguration can be applied to theDALI2 array to study in-beam γ-ray spectroscopy.
Fig. 1. New conﬁguration: (a) conceptional image; (b) insideof the vacuum chamber; (c) the size of the target cell.
∗1
∗2
∗3
∗4
∗5Research Center for Nuclear Physics, Osaka University
RIKEN Nishina Center
High Energy Nuclear Physics Laboratory, RIKEN
Department of Physics, University of Hong Kong
Department of Physics, Tokyo Institute of Technology- 93 -References
1) H. Ryuto et al., Nucl. Instrum. Methods Phys. Res. A555, 1 (2005).
2) Y. Togano et al., Nucl. Instrum. Methods Phys. Res. B
463, 195 (2020).
3) S. Koyama and D. Suzuki, RIKEN Acce. Prog. Rep. 52,148 (2019).