08/09/09 1

Working Group 2-2: Instrumentation, Nuclear Structure

The discussion in the instrumentation session was a sort of firstresponse to the ATLAS Intensity Upgrade by this part of the usercommunity.

The discussion also referred to the plans for Digital Gammasphere.

A personal note: A sub-aspect of future Gammasphere plans is theVME readout that would be also beneficial for external detectorsassociated with Gammasphere (so-called auxiliary detectors).

08/09/09 2

Presentations directly related to ATLAS intensity upgrade

Doug Cline, Rochester – “Chico experiments with Caribu beams”

Walter Reviol, Washington U. – “Towards Super Hercules andNanoball”

Andreas Heinz, Yale – “Prompt and delayed conversion electronspectroscopy of heavy nuclei”

Darek Seweryniak, ANL – “Gas-filled separator for nuclearstructure experiments at ATLAS

08/09/09 3

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)

Chico+Gammasherestable beam expt.

08/09/09 4

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%

Doug Cline

Higher segmentation compared to Chico → higher count rate

08/09/09 5

# det. elements (pixels) 64

Active fraction surface 0.89

Pixel size (mm2) 6x6

“Overall” light guide yes

8x8 Multianode PMT (Hamamatsu 8500)

The light guide is a 0.15-mmthick plastic sheet.

The PMT glass window causescross talk (established by tryingalso “individual” light guides).

The cross talk can be turned into an advantage (tracking).

Four PMT’s will be arranged in a “Gobi” geometry.

Super Hercules PrototypeReviol

08/09/09 6

PID Plot for Stilbene

Notice short charge-integration gates [50 x faster than CsI(Tl)].

97% pure material“home grown”

Reviol

Nanoball: PID needs only 130 ns (Microball: 8 μs)

08/09/09 7

Needs for Heavy Nuclei• High detection efficiency also at low

energies.• e-gamma, e-e, gamma-gamma correlations;

i.e. a spectrometer coupled to GAMMASPHERE/GRETINA.

• Channel selection (coupled to FMA)• Usable at high beam currents.

Andreas Heinz – “Prompt and delayed e- spectroscopy”

08/09/09 8

Needs for Delayed Conversion Electrons

• High detection efficiencies and resolution - especially at low electron energies.

• Alpha-electron coincidences• Electron-gamma coincidences

e spectrometer?

Recoils

Catcher (active?)

Ge

Ge

Degrader (active?) M. Asai et al., PRL 95, 102502 (2005)

253Fm

Andreas Heinz

08/09/09 9

Darek Seweryniak – “Gas filled separator”

10

Important design considerations

Large solid angle Good beam suppression Flexible and efficient coupling to GAMMASPHERE FRIB ready State-of-the art implantation facility (exists)

Heavy nuclei research– HK calorimetry – In-beam gamma and electron spectroscopy– K-isomers– Mass measurements

Heavy proton drip line nuclei

Flagship experiments on spectroscopy of heavy nuclei

08/09/09 11

Si Detectors and Si Avalanche Photodiodes

Con Beausang, Richmond – “Stars at Gammasphere”

Lakshmi Soundara Pandian, Lowell – “Towards NuclearSpectroscopy with a Position Sensitive Avalanche Photo Diode”

08/09/09 12

STARS-at Gammasphere?

d Beam @ 21&29 MeV

235U

E E1 E2

Clover (6 in all)

p

Fission-ESi Det

fis

Si Det

.5mm 1mm1mm.14mm

+12C**

**400 g/cm2 target with 12C backing

“raytrace”

48 Rings 16 Sectors

Con Beausang (p,t) reactionsNew needs for light ATLAS beams?

08/09/09 138th Aug 2009 ANL User Workshop

14 mm

< 200 m thick Si

four-corner design

charge fractionation

14 mm

K.S. Shah et al., IEEE Trans. Nucl. Sci.49(4), 1687 (2002).

(RMD, Inc.)

Dr. Pandian, 224Ra source measurements

Position sensitive avalanche photo diode

Possibility for particle-gammacorrelations

08/09/09 14

Kris Starosta

Geant simulations indicate 75% s.a. coverage

08/09/09 15

Plunger Recoil-Distance Devices, Moving Tape Collectors

Kris Starosta, NSCL – “Recoil distance method for lifetimemeasurements near N=Z line”

Umesh Garg, Notre Dame – “The Gammasphere Plunger”

Kim Lister, ANL – “The beta-decay station for Caribu”

08/09/09 16

Kim Lister – “beta-decay station”

08/09/09 17

Thanks for your attention!