CHICO experiments with CARIBU beamsD. Cline, A. Hayes, and C.Y. Wu

• CHICO: Designed to exploit Gammasphere for study of quasi-binary reactions

• Coulomb excitation

• Single and multi-nucleon transfer reactions

• Deep inelastic reactions

• Fission

• Motivation: Exotic neutron-rich beam physics motivation:

• Explore the evolution of collectivity and shell structure with isospin.

• Deep inelastic and transfer reactions will extend range of neutron-rich nuclei.

• Pair transfer to probe neutron pairing correlations in neutron-rich nuclei

• Exploit isomeric beams to probe unusual shell configurations

Ge detectorCHICO

Scattering angle: 12 85 (Front Part) 95 168 (Back Part)

Azimuthal angle total: 280 of 360 Position resolution: 1 in and 4.6 in

Solid angle: 69% of 4π Time resolution: 500 ps

Mass resolution Δm/m = 5%

CHICO*

M.W.Simon, D. Cline, C.Y. Wu

R.W. Gray, R. Teng. C. Long

Nucl. Inst. Meth. A452 (2000) 205

*Work supported by the NSF

Deep-inelastic products

Fission products

Deep-inelastic products

Fission products

CHICO Mass and Q-value

283.7 MeV 48Ca on 208Pb

S. Zhu, R.V.F. Janssens, et al, NS06, 2006

Doppler-corrected γ-ray spectra 1358 MeV 238U on 170Er

Raw data

Correction for

U-like recoils

Correction for

Er-like recoils

C.Y. Wu, D. Cline, et al, Phys. Rev. C61 (2000) 21305(R)

Coulomb excitation of 178Hf by 650 MeV 136XeA.B. Hayes1, D. Cline1, C.Y. Wu1, M.W. Simon1, R. Teng1, J. Gerl2, Ch. Schlegel2, H.J.Wollersheim2, A.O. Macchiavelli3, K. Vetter3, P. Napiorkowski4, J. Srebrny4

1)Rochester, 2)GSI, 3)LBNL, 4)Warsaw

Physical Review Letters 89 (2002) 242501

Triple γ-γ-γ spectrum gated on the 377keV (18+→17+) plus 398keV (19+→18+) peaks of the K=16+ isomer band in 178Hf for Coulomb excitation of a 178Hf beam by a 208Pb target

• Clean well-resolved spectra• Peak to background ratio ~100:1• Peak areas up to several thousand counts

Advantages of CHICO for CARIBU research• Large solid angle:Study weak exotic beams or low cross-section processes

• Large angular coverage: High kinematic coincidence efficiency Large range of impact parameters

• Angular and time resolution: Mass, Q-value resolution; high selectivity

• Achieve maximum Doppler-corrected γ-ray resolution for Gammasphere:

• Identify γ-rays from each fragment

• Very high count-rate capability: > 100kHz

• Hardness to radiation damage: 242mAm target (1.6 mCi, 1 MHz α’s, 500 kHz x-rays)

• High background suppression: Can adjust threshold to suppress light ions (p, d, α, C) Kinematic coincidence requirement

• Minimal mass: Minimal γ-ray absorption and Compton scattering

• Low initial and operational costs: Only 80 channels of electronics for 4,200 pixels Operational costs negligible

Staging CHICO for CARIBU researchAdvantages:

• CHICO operates with Gammasphere both stand-alone or at the FMA

• Initial set up time is 1 week,

• Reliable and trouble-free operation during month-long campaigns

• Minimal maintenance and costs required during operation

• Weak exotic beams should eliminate radiation damage to the foils.

Concerns:

• Sensitive to pilot error when operating vacuum controls.

• Requires expert knowledge to handle and change thin foils• Will require an ATLAS in-house Chico expert to support the Rochester group if

long running periods are scheduled

Future: SuperCHICO plus GRETINA

• Angular coverage: 20o ≤ θ ≤ 85o, 95o ≤ θ ≤ 160o; 280o in φ

• Angular resolution: Δθ = 1o, Δφ = 1.4o

• Solid angle: 66% of 4π

• Time resolution: Δt = 500ps

• Mass resolution for kinematic coincidence: Δm/m = 5%

• Q-value resolution: ≤ 20 MeV

• GRETA Doppler-corrected γ-ray resolution: ~ 0.3%

CHICO + Gammasphere portable data analysis codes

Data sorting and reduction: ANL Root-based GSSort (T. Lauritsen, S. Zhu) , Radware (Radford)

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GOSIA: Coulomb excitation least-squares search codes:Can fit <1000 electromagnetic matrix elements coupling 100 levels to thousands of Coulex data

1980: Fortran code originally developed at Rochester, (T. Czosnyka, D. Cline, C.Y. Wu)

2008-09: Major updates to methods and coding, (D. Cline, A. Hayes, P. Napiorkowski, N. Warr)The codes are more reliable, and robust using modern compilers. Input and operation simplified.The Gosia User Manual has been extensively revised, and expanded to facilitate use.

Download the latest versions of the suite of Gosia codes plus the User Manual available at Gosia web site:http://www.pas.rochester.edu/~cline/Gosia/index.html

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CAP Congress Saskatoon, 18 June 2007 Douglas Cline for TIGRESS Collaboration

Bambino Si CD Heavy-ion detector(LLNL; Rochester)

• Forward and backward annular Si CD heavy-ion detectors

• Angular coverage:

20o < θ < 50o, 130o < θ < 160o

00 < φ < 315o

• Angular resolution;

Δθ = 1.22o, Δφ = 22.5o

http://www.pas.rochester.edu/~cline/Research/index.html

Summary of CHICO performance• Angular coverage: 12o ≤ θ ≤ 85o, 95o ≤ θ ≤ 168o; 280o in φ

• Angular resolution: Δθ = 1o, Δφ = 9.3o

• Solid angle: 69% of 4π

• Time resolution:Δt = 500ps

• Mass resolution for kinematic coincidence: Δm/m = 5%

• Q-value resolution: ≤ 20 MeV

• Gammasphere Doppler-corrected γ-ray resolution: ≥ 0.8%

Further information about CHICO available at http://www.pas.rochester.edu/~cline/Research/index.html

Coulomb excitation of 1360 MeV 238U by 208PbM.W. Simon, D. Cline, C.Y. Wu, R. Teng, K. Vetter, M.P. Carpenter, R.V.F. Janssens, I. Wiedenhover