TPC for 2p radioactivity studies

Bertram Blank, CENBG

1

0 0 1 2 3 4 5 6

Energy (MeV)

four 2p decay events

GSI

GANIL

Discovery of two-proton radioactivity

However: - only decay energy- no individual energies- no proton-proton angle

TPC

- individual energies- proton-proton angle

Daughter boards

Hybrid boards

GEM: Gas electron multiplierbeam

1500 electronics channels

Hybrid boards

Daughter boards

x

z

Cathodes:-768 micros-strips of copper (200m)

Anodes:-768 micros-strips of copper on a capton substrate (2x100m)-Epoxi frame

y

x

Mother board

+ detector (15x15 cm2)

+ 3 GEMs

y

x

x

z

TPC chamber

Detector mount

Detector mount

Electronics card

Strip-strip matrix

GEM

= 70md = 100m

x energy | x time | y energy | y time

Implantation at entrance Implantation at end

saturation

Different implantation depths by changing the B

Entrance of TPC Center of TPC End of TPC

Threshold for implantation events

Threshold for radioactivity events

48Ca + 9Be 26P, 25Si,….

x

y

beam

Silicon detector

x energy | x time | y energy | y time

Collimated source -delayed decay

-delayed decay -delayed decay

x

y

beam

Silicon detector

Detector: double-sided microstrip detector (CERN)

GEM: Gas electron multiplier (CERN)

Detector gas: P10 at 1atm

Active detection volume: 15 x 15 x 15 cm3

ASICS: VAT/TAT by IDEAS, Norway

TAC window: 10 s

channels per chip: 32 time and energy

Electronics and data acquisition: PXI – VME

Dead time: 1.5 ms (max)

4 GEMs to increase the gain

new a source collimation system

non-linearity of the gain (-30% on sides)

retract drift frames

20 mm

30 mm

28 mm

beam

-17%

-33%

Top view

Possible reason:

drift frames for field homogeneities

GEM spectra

• two-proton radioactivity: 45Fe, 54Zn, 59Ge ?• 2p radioactivity: 22Al, 23Si, 26P, 27S, 31Ar,…..• correlations ????• ???

• CENBG: Exotic nuclei group Electronics group Intrumentation group Mechanics group• GANIL: DAQ group LISE group