Present and future limitations of SHE in-beam experiments

R-D Herzberg

Outline

Decay studies Equipment Present bottlenecks

– Separator– Spectrometer– DAQ

Sample calculatons

In-beam studies Equipment Present bottlenecks

– Target– Spectrometer– Recoil ID– DAQ

Sample calculations– 253No, 256Rf, 260Sg

Decay Studies (high beam: 10 pµA)

Target: (Sigurd)– Temperature!

Separator: (Sigurd)– Cleanliness– Transmission– Recoil Identification

Instrumentation

Equipment

GREAT – type spectrometer

Sensitivity to all emitted radiation

Clean Recoil ID DAQ: Triggerless to

avoid correlation losses due to deadtime

Bottlenecks

Geometric efficiencies– Active tape (moving Si)– Can yield extra 25 %

over “tunnel” designs– Very clean– Might induce losses for

short primary times.

Preamplifiers with large dynamic range required (Recoil -> Alpha -> CE)

Bottlenecks II

Ge detectors: – Close geometry– Sensitivity to X-rays

Conversion electrons– Low thresholds on all Si– Thick Si required

DAQ

Must be able to handle a large number of channels

Common deadtime approaches not really suitable -> triggerless DAQ!

Short decays (µs) require digital cards to allow distinction

Sample calculation 261Bh

209Bi(54Cr,2n)261Bh XS ~ 0.1 nb (NPA273 (76) 505)

To do spectroscopy of 257Db one needs to see >1000 alpha decays

Separator efficiency 60% Br(alpha) = 100% 21 days at 1000 pnA -> straightforward If XS 10 pb and beam 5000 pnA 42 days

(marginal)

Conclusions

No insurmountable problems at the focal plane.

Spectroscopy after alpha decay is an excellent way to identify single particle structure in SHE

Possible down to 10 pb

In-beam Studies

Experience with gamma and CE studies Unique set of problems Main challenge is Fission

Equipment

Target (Wheel) Prompt Spectrometer capable of high rate Separator with large transmission Excellent Recoil ID DAQ capable of high rate

Gamma Ray spectrometer

Dominant channel is constant ~0.1 - 1b Fission. This limits Ge rate!

Target wheel spokes need beam sweeping High granularity and large distance to keep

individual rates low (Jurogam, Euroball) Background from entrance windows etc.

– Need windowless system!

Electron Spectrometer

Fission does not readily procuce CE SHE produce more CE than Gamma

Delta electrons require HV barrier Generally difficult Rate concentrated near field axis Baseline dirty -> need digital cards

SACRED

At present, electron experimentsUse 20% of the beam current of Gamma experiments.

Rate adjustable with HV barrier.

Targets need to be thinner (0.25 mg/cm2)

Recoil ID

Mainly the task of the separator

Scattered beam

Fm recoils

Rate calculation basics

10 pnA on 500 µg/cm2 at 1 µb = 325 Reactions/h At maximum XS ~20 ħ in the system Fission rates adjusted to match experimentally

observed Ge rates, then scaled Two spectrometers: 5% and 10% Efficiency

e.g. Jurogam or Euroball

Bottlenecks

Ge rate. Present: 10 kHz/detector With digital electronics and high throughput

preamplifiers: 30 kHz/detector, eventual aim is 100 kHz/detector

DAQ must handle these rates to preprocess and write to tape. Data rates up to 50MB/s– BGO suppression– Recoil coincidence

Sample calculationsN

uc

leu

s

Th

ick

ne

ss

I_B

ea

m

X S

ec

t

Re

ac

/h

No

de

t

Eff

G/h

T_

tot

Fis

s/s

Ga

mm

ab

g/s

Ge

_ra

te

Da

tara

te

Tra

ns

mis

sio

n

(ug

/cm

^2

)

(pn

A)

(nb

)

% de

tec

ted

(da

y)

(kH

z)

raw

(M

B/s

)

%

254No 500 10 2000 650 45 5 41 5 90000 134996 3000 1 25253No 500 10 1000 325 45 5 20 10 90000 134996 3000 1 25252No 500 20 220 143 45 5 9 23 180000 269991 6000 2 25256Rf 500 150 5 24 200 10 7 29 1350000 4046392 20232 31 60260Sg 500 210 0.28 2 200 10 1 365 1890000 5664948 28325 43 60

Conclusions

Decay studies will be possible without large changes to existing detector technology and electronics. Target/Separator are crucial.

In-beam studies will need highest rate capabilities – electronics, DAQ. Target must allow the beam, 1 nb level possible.