Status of SπRIT-TPC

M. Kurata-Nishimura,∗1 R. Shane,∗2 A. McIntosh,∗3 T. Isobe,∗1 J. Barney,∗2 J. Estee,∗2 G. Jhang,∗1∗4

W. Powell,∗5 W.G. Lynch,∗2 M.B. Tsang,∗2 T. Murakami,∗6 S. Tangwancharoen,∗2 S.J. Yennello ,∗3

for SπRIT-TPC collaboration

The SAMURAI Pion-Reconstruction and Ion-Tracker Time-Projection Chamber (SπRIT-TPC)1)

was constructed at Michigan State University andtransferred to RIKEN RIBF-SAMURAI in February2014. The main aim of this project is to constrainthe symmetry energy term in the nuclear-matter equa-tion of state (EoS) at supra-saturation density. TheSπRIT-TPC is capable measuring the momentum ofpions and light particles emitted in heavy nuclear col-lisions, such as 132Sn + 112Sn at beam energies of hun-dreds of MeV/nucleon.

In summer 2014, an installation procedure for theSπRIT-TPC into the SAMURAI magnet chamber wasdeveloped and verified. The SπRIT-TPC is designedto maximize the coverage in the SAMURAI magnetchamber. The internal height of SAMURAI chamber isdesigned to be 800 mm. Bolts, covered by 25 mm highcaps, surround the magnet pole on top and bottom toprevent the chamber from crushing due to the pressuredifference when the chamber is under vacuum. On theother hand, the design height of the SπRIT-TPC is742 mm and thus there is a very small margin of errorfor installing it into the SAMURAI chamber. Thusthe confirmation of the installation is one of the mostimportant issues in this project. Also confirmation ofsafe operation in the magnetic field is critical.

The setup for installation of the SπRIT-TPC in thechamber is shown in Fig.1. In this figure, the SAMU-RAI magnet was oriented at 30 degrees, it is most com-mon experimental configuration. However, the SpiRITTPC was designed to sit inside the SAMURAI magnetchamber when it is oriented at zero degree. To testthe installation procedure without expending a lot ofresources to reconfigure the SAMURAI magnet, theSπRIT-TPC was inserted from one half side of theexit window with the oblique angle. Rails placed inthe chamber extended toward the downstream win-dow where additional rails were located on tables. TheSπRIT-TPC was set on a slider which moves alongrails with negligible friction. It was able to be pushedand pulled in the chamber using dual hydraulic jacks.When the SπRIT-TPC was installed inside the cham-ber, it was raised up about 25 mm to the beam height.Installing and dismounting the SπRIT-TPC was com-

∗1 RIKEN Nishina Center∗2 National Superconducting Cyclotron Laboratory and De-

partment of Physics and Astronomy, Michigan State Uni-

versity∗3 Cyclotron Institute, Texas A&M University∗4 Department of Physics, Korea Universtiy∗5 Department of Physics, University of Liverpool∗6 Department of Physics, Kyoto University

pleted in about 20 minutes.An operational test in the magnetic field was also

performed. Before hand, all magnetic material itemson the SπRIT-TPC were removed. The read outelectronics described in Ref.2) were set up. Finally,charged particle tracks of cosmic rays and beta sourcewere detected in a magnetic field ranging from 0.1 to0.5 T. Figure 2 shows a part of a helical track producedby a cosmic ray was observed within the detection arearead out by one AsAd electronics board.

Furthermore, a remote controlled target ladder wasmounted inside the TPC-enclosure. The target posi-tion is determined by reading the voltage drop betweenthe fixed and movable contacts on a resistive strip.

The overall geometry and position of the field cageand the target ladder relative to the enclosure weremeasured using photogrammetry2). The deviationfrom the design value was evaluated as less than 200µm.

In summary, significant progress on the preparationfor the SπRIT-TPC experiment has been achieved.

Fig. 1. Picture of the SπRIT-TPC inserted into the SAMU-

RAI chamber. Left top: picture in the chamber. Left

bottom: schematic view of the installation method.

Fig. 2. Event display for a cosmic ray detected by the

SπRIT-TPC in the SAMURAI magnet at 0.3 T. En-

larged view of the track is on the right.

References1) R. Shane at al.: Nucl. Instr. Meth. A 784 (2015) 513.2) http://www.geodetic.com/products/systems/v-stars-s.aspx3) T. Isobe et al.: in this report.

Test of prototype crystals of the γ-ray detector CATANA

Y. Togano,∗1,∗2 M. Shikata,∗1 T. Ozaki,∗1 Y. Kondo,∗1,∗2 and T. Nakamura∗1,∗2

The γ-ray detector CATANA (CAesium iodide ar-ray for γ-ray Transitions in Atomic Nuclei at highisospin Asymmetry) has been developed to measureγ ray associated with highly excited states like thepygmy dipole resonance and/or giant dipole resonance.CATANA will be used with SAMURAI at RIBF.1) Theexcitation energy will be reconstructed by combiningthe invariant mass of the reaction products measuredby SAMURAI and γ-ray energies from CATANA.The CATANA array consists of CsI(Na) crystals and

has between 10 and 15 cm thickness. The crystals arehoused in 0.5-mm-thick aluminum boxes. The photo-sensors for the scintillation light from the crystals arethe photo multiplier tubes (PMTs) R580 and R11265from Hamamatsu Photonics. A detailed description ofCATANA can be found in ref.2).

The position dependence of light collection efficiencycan be significant for the crystals of CATANA, becausethe crystals have relatively large volumes. We havetested the position dependence of the light collectionefficiency of the prototype CsI(Na) crystals by using γrays from 137Cs, 22Na, and 60Co sources. The geome-try of the tested crystals is shown in Fig. 1. To eval-uate the position dependence, the collimated γ raysirradiated the crystals from a direction perpendicularto the x − z plane defined in Fig. 1. The collima-tor was a 10 cm thick lead with a 1-cm-diameter hole.The test was performed for two crystals from differ-ent companies. The two crystals have almost identicalgeometry. We tentatively name the two crystals as Aand B in this report. Figure 2 shows the typicalresponse of the crystals A and B to the uncollimated511 and 1275 keV γ rays from 22Na. Crystal A hasa better energy resolution than crystal B. The posi-tion dependence of the light collection efficiency alongcrystal length z of the crystals A and B to the γ rays

Fig. 1. Geometry of the tested prototype crystals. The

definition of the axis in the test is also shown. PMT

was attached to the top of the crystals.

∗1 Department of Physics, Tokyo Institute of Technology∗2 RIKEN Nishina Center

from 22Na is shown in Fig. 3. The light output of thecrystal B is larger at larger z. This tendency is due tothe optical focusing caused by the reflection of lights atthe polished surface of crystal B3). To obtain a betterposition dependence and energy resolution, changes inthe reflectivity of the crystal A surfaces were realizedby roughening the crystal surfaces.

The fabrication of the CsI(Na) crystals for CATANAwill start in spring 2015, and finish in late 2015.

References1) T. Kobayashi et al.: Ncul. Instrum. and Meth. B 317,

294 (2013).2) Y. Togano et al.: RIKEN Accel. Prog. Rep. 47, 179

(2014).3) J. Bea et al.: Nucl. Instrum. and Meth. A 350, 184

(1994).

Fig. 2. Typical response of the crystals to the 22Na source.

Fig. 3. Position dependence of the light collection efficiency

for the crystals A (red) and B (black) along the crystal

length z. Crystal B shows larger position dependence

of the light collection efficiency.

Test of prototype crystals of the γ-ray detector CATANA

Y. Togano,∗1,∗2 M. Shikata,∗1 T. Ozaki,∗1 Y. Kondo,∗1,∗2 and T. Nakamura∗1,∗2

The γ-ray detector CATANA (CAesium iodide ar-ray for γ-ray Transitions in Atomic Nuclei at highisospin Asymmetry) has been developed to measureγ ray associated with highly excited states like thepygmy dipole resonance and/or giant dipole resonance.CATANA will be used with SAMURAI at RIBF.1) Theexcitation energy will be reconstructed by combiningthe invariant mass of the reaction products measuredby SAMURAI and γ-ray energies from CATANA.The CATANA array consists of CsI(Na) crystals and

has between 10 and 15 cm thickness. The crystals arehoused in 0.5-mm-thick aluminum boxes. The photo-sensors for the scintillation light from the crystals arethe photo multiplier tubes (PMTs) R580 and R11265from Hamamatsu Photonics. A detailed description ofCATANA can be found in ref.2).

The position dependence of light collection efficiencycan be significant for the crystals of CATANA, becausethe crystals have relatively large volumes. We havetested the position dependence of the light collectionefficiency of the prototype CsI(Na) crystals by using γrays from 137Cs, 22Na, and 60Co sources. The geome-try of the tested crystals is shown in Fig. 1. To eval-uate the position dependence, the collimated γ raysirradiated the crystals from a direction perpendicularto the x − z plane defined in Fig. 1. The collima-tor was a 10 cm thick lead with a 1-cm-diameter hole.The test was performed for two crystals from differ-ent companies. The two crystals have almost identicalgeometry. We tentatively name the two crystals as Aand B in this report. Figure 2 shows the typicalresponse of the crystals A and B to the uncollimated511 and 1275 keV γ rays from 22Na. Crystal A hasa better energy resolution than crystal B. The posi-tion dependence of the light collection efficiency alongcrystal length z of the crystals A and B to the γ rays

Fig. 1. Geometry of the tested prototype crystals. The

definition of the axis in the test is also shown. PMT

was attached to the top of the crystals.

∗1 Department of Physics, Tokyo Institute of Technology∗2 RIKEN Nishina Center

from 22Na is shown in Fig. 3. The light output of thecrystal B is larger at larger z. This tendency is due tothe optical focusing caused by the reflection of lights atthe polished surface of crystal B3). To obtain a betterposition dependence and energy resolution, changes inthe reflectivity of the crystal A surfaces were realizedby roughening the crystal surfaces.

The fabrication of the CsI(Na) crystals for CATANAwill start in spring 2015, and finish in late 2015.

References1) T. Kobayashi et al.: Ncul. Instrum. and Meth. B 317,

294 (2013).2) Y. Togano et al.: RIKEN Accel. Prog. Rep. 47, 179

(2014).3) J. Bea et al.: Nucl. Instrum. and Meth. A 350, 184

(1994).

Fig. 2. Typical response of the crystals to the 22Na source.

Fig. 3. Position dependence of the light collection efficiency

for the crystals A (red) and B (black) along the crystal

length z. Crystal B shows larger position dependence

of the light collection efficiency.

Test of prototype crystals of the γ-ray detector CATANA

Y. Togano,∗1,∗2 M. Shikata,∗1 T. Ozaki,∗1 Y. Kondo,∗1,∗2 and T. Nakamura∗1,∗2

The γ-ray detector CATANA (CAesium iodide ar-ray for γ-ray Transitions in Atomic Nuclei at highisospin Asymmetry) has been developed to measureγ ray associated with highly excited states like thepygmy dipole resonance and/or giant dipole resonance.CATANA will be used with SAMURAI at RIBF.1) Theexcitation energy will be reconstructed by combiningthe invariant mass of the reaction products measuredby SAMURAI and γ-ray energies from CATANA.The CATANA array consists of CsI(Na) crystals and

has between 10 and 15 cm thickness. The crystals arehoused in 0.5-mm-thick aluminum boxes. The photo-sensors for the scintillation light from the crystals arethe photo multiplier tubes (PMTs) R580 and R11265from Hamamatsu Photonics. A detailed description ofCATANA can be found in ref.2).

The position dependence of light collection efficiencycan be significant for the crystals of CATANA, becausethe crystals have relatively large volumes. We havetested the position dependence of the light collectionefficiency of the prototype CsI(Na) crystals by using γrays from 137Cs, 22Na, and 60Co sources. The geome-try of the tested crystals is shown in Fig. 1. To eval-uate the position dependence, the collimated γ raysirradiated the crystals from a direction perpendicularto the x − z plane defined in Fig. 1. The collima-tor was a 10 cm thick lead with a 1-cm-diameter hole.The test was performed for two crystals from differ-ent companies. The two crystals have almost identicalgeometry. We tentatively name the two crystals as Aand B in this report. Figure 2 shows the typicalresponse of the crystals A and B to the uncollimated511 and 1275 keV γ rays from 22Na. Crystal A hasa better energy resolution than crystal B. The posi-tion dependence of the light collection efficiency alongcrystal length z of the crystals A and B to the γ rays

Fig. 1. Geometry of the tested prototype crystals. The

definition of the axis in the test is also shown. PMT

was attached to the top of the crystals.

∗1 Department of Physics, Tokyo Institute of Technology∗2 RIKEN Nishina Center

from 22Na is shown in Fig. 3. The light output of thecrystal B is larger at larger z. This tendency is due tothe optical focusing caused by the reflection of lights atthe polished surface of crystal B3). To obtain a betterposition dependence and energy resolution, changes inthe reflectivity of the crystal A surfaces were realizedby roughening the crystal surfaces.

The fabrication of the CsI(Na) crystals for CATANAwill start in spring 2015, and finish in late 2015.

References1) T. Kobayashi et al.: Ncul. Instrum. and Meth. B 317,

294 (2013).2) Y. Togano et al.: RIKEN Accel. Prog. Rep. 47, 179

(2014).3) J. Bea et al.: Nucl. Instrum. and Meth. A 350, 184

(1994).

Fig. 2. Typical response of the crystals to the 22Na source.

Fig. 3. Position dependence of the light collection efficiency

for the crystals A (red) and B (black) along the crystal

length z. Crystal B shows larger position dependence

of the light collection efficiency.

Test of prototype crystals of the γ-ray detector CATANA

Y. Togano,∗1,∗2 M. Shikata,∗1 T. Ozaki,∗1 Y. Kondo,∗1,∗2 and T. Nakamura∗1,∗2

The γ-ray detector CATANA (CAesium iodide ar-ray for γ-ray Transitions in Atomic Nuclei at highisospin Asymmetry) has been developed to measureγ ray associated with highly excited states like thepygmy dipole resonance and/or giant dipole resonance.CATANA will be used with SAMURAI at RIBF.1) Theexcitation energy will be reconstructed by combiningthe invariant mass of the reaction products measuredby SAMURAI and γ-ray energies from CATANA.The CATANA array consists of CsI(Na) crystals and

has between 10 and 15 cm thickness. The crystals arehoused in 0.5-mm-thick aluminum boxes. The photo-sensors for the scintillation light from the crystals arethe photo multiplier tubes (PMTs) R580 and R11265from Hamamatsu Photonics. A detailed description ofCATANA can be found in ref.2).

The position dependence of light collection efficiencycan be significant for the crystals of CATANA, becausethe crystals have relatively large volumes. We havetested the position dependence of the light collectionefficiency of the prototype CsI(Na) crystals by using γrays from 137Cs, 22Na, and 60Co sources. The geome-try of the tested crystals is shown in Fig. 1. To eval-uate the position dependence, the collimated γ raysirradiated the crystals from a direction perpendicularto the x − z plane defined in Fig. 1. The collima-tor was a 10 cm thick lead with a 1-cm-diameter hole.The test was performed for two crystals from differ-ent companies. The two crystals have almost identicalgeometry. We tentatively name the two crystals as Aand B in this report. Figure 2 shows the typicalresponse of the crystals A and B to the uncollimated511 and 1275 keV γ rays from 22Na. Crystal A hasa better energy resolution than crystal B. The posi-tion dependence of the light collection efficiency alongcrystal length z of the crystals A and B to the γ rays

Fig. 1. Geometry of the tested prototype crystals. The

definition of the axis in the test is also shown. PMT

was attached to the top of the crystals.

∗1 Department of Physics, Tokyo Institute of Technology∗2 RIKEN Nishina Center

from 22Na is shown in Fig. 3. The light output of thecrystal B is larger at larger z. This tendency is due tothe optical focusing caused by the reflection of lights atthe polished surface of crystal B3). To obtain a betterposition dependence and energy resolution, changes inthe reflectivity of the crystal A surfaces were realizedby roughening the crystal surfaces.

The fabrication of the CsI(Na) crystals for CATANAwill start in spring 2015, and finish in late 2015.

References1) T. Kobayashi et al.: Ncul. Instrum. and Meth. B 317,

294 (2013).2) Y. Togano et al.: RIKEN Accel. Prog. Rep. 47, 179

(2014).3) J. Bea et al.: Nucl. Instrum. and Meth. A 350, 184

(1994).

Fig. 2. Typical response of the crystals to the 22Na source.

Fig. 3. Position dependence of the light collection efficiency

for the crystals A (red) and B (black) along the crystal

length z. Crystal B shows larger position dependence

of the light collection efficiency.

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