# Presentation: 655584

## Status of CNS GRAPE and γ-ray spectroscopy community in Japan

- Eiji Ideguchi
- CNS, University of Tokyo

## Status of GRAPE

## Members

- CNS
- S. Shimoura (P)
- E. Ideguchi (L)
- S. Ota (PD)
- M. Niikura (D3)
- H. Miya(B4)

- CNS collaborators
- T. Fukuchi (RIKEN)
- M. Kurokawa (RIKEN)
- S. Michimasa (CNS)
- H. Baba (RIKEN)

- CNS-UT-RIKEN-Rikkyo-
- -Kyoto... Collaboration

## 18x2 segmented Ge detectors

- High Resolution
- 2.5 keV intrinsic resolution for 1.3 MeV 
- High Sensitivity
-  ~ 5 % for 1 MeV 
- Position Sensitive
- Resolution of Doppler Correction ~ 1 %

- GRAPE  (Gamma-Ray detector Array with Position and Energy sensitivity)

- Goal: 1mm position resolution for z-direction

**Notes:**
CNS Ge array consists of 18 detectors.
Each detector has two segmented Ge crystals and placed inside hexagonal capsule and here is 18 preamplifiers with FETs at room temperature.
This part is liquid nitrogen dewar.
Detector has 2.5keV intrinsic resolution for 1.3 MeV gamma ray.
It is designed to have the efficiency of 5% for 1MeV gamma ray
And position resolution of 1 mm for z-direction.
With this position resolution, 1% of energy resolution for 1MeV
Gamma ray after Doppler correction.

## Reactions for the study of excited states

- Direct Reactions (>30 MeV/u)
- Heavy Nuclei: Strong Coulomb Field
- Coulomb Excitation, Coulomb Dissociation
- E1, E2, (M1) / Isovector
- H, D, 4He [Liquid targets]
- Inelastic Scattering
- Isovector (H) / Isoscaler(H, D, **4****He**)
- Spin-Flip (H, D) / Spin-Non-Flip (H, D, **4****He**)
- Charge Exchange
- Fermi type (H) / Gamow-Teller type (H, D)
- Nucleon Transfer
- (a,t), (a,3He) Reaction
- Knockout
- Other (Be, C, ...)
- Knockout / Fragmentation
- Spectroscopic Factor / States with various Spin
*Fusion (& Multiple Coulex, Deep inelastic) (<20 MeV/u)*
*High Spin States*

- Liquid target

- Low multiplicity

- High multiplicity

**Notes:**
Here is some typical reactions we use for the study of excited states.
In case beam energy is grater than 30 MeV/nucleon, we can use direct reactions 
using thick target. Solid target as well as liquid targets such as Liquid He and liquid
H are available. 
In the case of beam energy is less than 20MeV/nucleon, we can do
fusion reactions and Deep inelastic reactions using secondary beam.

## Z-Position (~ )  

- Z-Position (~ ) 
- Drift length of electrons and holes

- P-type, ~0.8x1010 cm-3

- Z

- ρ

- ⊿β=0.01:
-  50AMeV 12Be + 250mg/cm2 Be
-  50AMeV 32Mg + 70mg/cm2 Be
-  50AMeV 68Ni + 30mg/cm2 Be
- 200AMeV 68Ni + 200mg/cm2 Be

## Pulse Shape vs. Pos.

- (CR)2-(RC)4
- shaping

**Notes:**
This figure schematically shows the relation between pulse shape and hitting position of gamma rays inside Ge crystal. 
Right panel schematically shows pulse shapes from segmented cathodes of a planar detector for two cases of the interaction points making the electron-hole pairs near cathode (left) and near anode (right).
Same constant drift velocities for electrons and holes are assumed for simplicity.
The labels “A or C”, “B”, and “A+ B+C” indicate signals from corresponding cathodes and sum of all cathodes, respectively.
Red lines and green lines denote the contributions of electrons and holes, respectively.
As shown in the figure, the sum signals of “A+B+C” are identical for the two cases although contributions from electrons and holes are different.
The rise time of the signal changes at the time when the holes or electron arrived at cathodes or anode.
Signals from “B” are different shapes for the two cases because of opposite polarity of the “A or C” signals.
These features in the pulse of “sum” and “hit” signals are used for the determination of the depth of interactions.
This difference in pulse shape can be picked up as a zero-cross timings after (CR)2-(RC)4 shaping of the sum and hit signals.

Left panel shows the pulse shapes of segment 5 (central segment) and sum of all segments.
Pulse shapes of preamplifier and that after (CR)2-(RC)4 shaping.
By picking up these zero cross timings by using zero-cross discriminator, we can extract the difference of pulse shapes.

## Block diagram

- Sum Amp

- Fast Amp

- Differentiation×2

- Pre Amp×9×2

- S. Amp

- Σ

- Ind.

- Zero cross
- disc.

- TDC

- ADC

- GRAPE

- Segment

- Sum

- M. Kurokawa et al.,
- IEEE Trans. Nucl. Sci. , 50(2003)1309

- Central segment

- Side segments

- Corner segments

- Tsum – (Thit-Tsum)

## 4He(12Be,13Bγ)

- JPS 2007s

- 4He(12Be,13Bγ)

**Beam tracker**
**Position and direction**

**Gamma-ray**
**detector**

**Charged particle detector**
**Plastic scintillator**
**ΔE, E, and position**

- Beam
- 12Be 50*A*MeV
- 200kcps
- 55% purity
- Target
- Liquid Helium
- 140mg/cm2

- Doppler shift: 30%
-   β~0.3 θ~140°
- 1.3% (FWHM) for 2.1MeV

- F2Pl

**Incident particle**
**identification**

## Pulse Shape Analysis

## Doppler correction using PSA

- 4He(12Be, 12Beγ)

- 2107keV

- After Doppler correction without
- PSA: take center of each detector
- As detector position and used fixed θ

- After Doppler correction with PSA

- FWHM~1.3%

- FWHM~1.8%

- 12Be : 49MeV/A at center of target
- Target: Liq.He 143mg/cm2

## z (FWHM) ~ 3.4 mm

- =0.3

- *z* (FWHM) ~ 3.4 mm

**Notes:**
This figure shows the gamma ray spectrum obtained in 4He(12Be, 12Be) reaction.
Inset shows the Doppler corrected spectrum without pulse shape information.
After using pulse shape information we can make narrower peak width.
This corresponds to about 3.4 mm of position resolution.
With this improved energy resolution, we also succeed to observe 1- to 0+ transition.

## Doppler Correction with Energy Degraded beam

- X : 17 mm ()
- Y : 8 mm ()

- 2-6 A MeV

## Special setup

- Life time measurement by
- Recoil Distance Method:
- GRAPE with BGO
- R400n, M.Suzuki et al.

- β –γ spectroscopy by using GRAPE + Clover Ge
- R396n, T.K.Onishi et al.

- ε(1MeV) ~ 3%

- Spacer

- Au degrader
- 190mg/cm2

- Au target
- 1.35g/cm2

## Without BGO

- With BGO

- Downstream

- Upstream

- S/N ratio is improved
- Factor 2.5

- 32Mg

- 885keV

## Efficiency curve

## GRAPE at RIBF

- With RIPS

- With BigRIPS+ZDS

- With BigRIPS
- +SHARAQ

- With AVF
- (Stable beam)

## Gamma-ray spectroscopy community in Japan

## Low-energy beam facility in Japan

- Major places for γ-ray spectroscopy

- Osaka, RCNP
- AVF cyclotron
- 14 coaxial Ge array
- Isomer spectroscopy

- Wako, Saitama
- CNS: GRAPE (18 segmented Ge)
- RIKEN: AVF cyclotron,
-               Ring cyclotron,  RIBF

- JAEA + KEK-TRIAC
- Tandem accelerator + booster
- GEMINI-II (16 Coaxial Ge with BGO ACS) and other Ge’s

- CYRIC, Tohoku University
- K130 AVF Cyclotron
- Hyperball-2 (6 Clover Ge and 14 coaxial Ge with BGO ACS)

## Japanese Gamma-ray Spectroscopy Association (JGSA)

- Started from March 2007.
- Purpose
- Exchange information between research groups
- Develop collaborative research activities
- Experimentalists ⇔ Experimentalist ⇔ Theorist
- → To define strategic target of this community (Detector, Physics, etc.)
- Present Organizers
- E. Ideguchi (CNS, Chair), N. Aoi (RIKEN), A. Odahara (Osaka),
-      T. Koike (Tohoku), T. Nakatsukasa (RIKEN)
- Web: _[http://www.cns.s.u-tokyo.ac.jp/gamma/](http://www.cns.s.u-tokyo.ac.jp/gamma/)_
- Now it appears in Japanese language.
- Internationalization will be discussed.
- Mailing-list: _[gamma-ml@mail.cns.s.u-tokyo.ac.jp](mailto:gamma-ml@mail.cns.s.u-tokyo.ac.jp)_

## Numbers of registered members: 51 (as of Jan. 24, 2008)

- Experimentalists: 42, Theorists: 9
- Affiliation: 3 Institutes  and 10 Universities
- CNS, RIKEN, JAEA, KEK, Tokyo, Tohoku, Osaka, Kyoto, Kyushu, Niigata, Saitama, Chiba, Chiba Inst. Tech., Tokyo Univ. Sci.
- Regular meetings
- At biannual JPS meeting (Spring and Fall)
- 1st Meeting: March 26, 2007 @ Tokyo Metropolitan Univ.
- Kickoff meeting
- 2nd Meeting: Sep. 22, 2007 @ Hokkaido Univ.
- Exchange Information between groups (11 groups)
- Discussion about future collaboration
- 3rd Meeting: March 23, 2008 @ Kinki Univ.
- Exchange Information between groups
- Collaboration development

## CNS-RIKEN Joint International Symposium onFrontier of gamma-ray spectroscopy and Perspectives for Nuclear Structure Studies (gamma08)

- Date: April 3-5, 2008
- Place: Nishina Hall in RIKEN Wako Campus
- Organizers: E. Ideguchi (CNS, Chair), N. Aoi (RIKEN), S. Michimasa (CNS),
- H. Scheit (RIKEN), A. Odahara (Osaka), T. Koike(Tohoku), T. Ishii(JAEA),
- T. Nakatsukasa(RIKEN), S. Shimoura(CNS), T. Motobayashi(RIKEN),
- T. Otsuka(CNS/Tokyo)

- Main topics to be discussed are:* Collectivities and shell effects in neutron/proton-rich nuclei * Shell structure and stability of very heavy nuclei * Exotic deformation / new collective motion at low and high spin * Single particle motion in isomeric states * Development of detectors and experimental methods
- Web: _[http://www.cns.s.u-tokyo.ac.jp/gamma08/](http://www.cns.s.u-tokyo.ac.jp/gamma08/)_     → Registration, abstract
- Deadlines* Deadline for abstract submission: February 15, 2008* Deadline for registration: March 21, 2008