Test of PRISMA in Gas Filled Mode
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Transcript of Test of PRISMA in Gas Filled Mode
Test of PRISMA in Gas Filled ModeB.Guiot for PRISMA collaboration
INFN – Laboratori Nazionali di Legnaro
Measurements of small fusion cross sections are experimentally challenging
Motivation
C.L. Jiang et al., Phys. Rev. Lett. 89 052701 (2002) : 60Ni+89Y
C.L. Jiang et al., Phys. Rev. Lett. 93 012701 (2004) : 64Ni+64Ni
Example: the hindrance phenomenon
Principles of operation of a gas-filled magnetic spectrometer
Charge states merge
q
mvB
vZq
to a first approximation, B does not depend on v
vacuum gas
Poor resolution (no single mass resolution) Basically a high-efficiency separator Typically operated at 0° for the detection of fusion evaporation residues
Problems with magnetic rigidity
Magnetic rigidity
0,5
0,7
0,9
1,1
1,3
1,5
1,7
1,9
0,01 0,10 1,00 10,00E/A (MeV/amu)
B
(Tm
)
58Ni
112Sn
148Sm
176Hf
208Pb
252Fm
<q> according to Betz
The average charge state can be very low in gas for a slow, heavy ion
for a central trajectory Prisma is limited to A<180
By using non-central trajectory we can reach B=1.5Tm
TmB 2.1
Prisma max. rigidity for central trajectory
Magnetic rigidity of Evaporation Residues
Projectile and ER rigidity as a function of the target Z @ E=VB
for all practical cases
ERBEAM BB
Forget reverse kinematics!
S
Ni Ca
Se
1.5Tm
projectile
CN
3230 mm
800 mm
EFB
EFB
GFM operation of Prisma. General considerations
the drift-chamber + detectors can move back 70cm and more
Drift chamber not to be operated in gas: • mult.scattering with no focusing elements• cannot optimize gas pressure in magnets
Gas filling: 4He is the most popularbut other gases should be tested
detector
C-foil window
Gate valve
Gas filling
EFB
EFB
1.2Tm
The setup for the GFM operation of Prisma
Prisma at 0°
1.5TmDRIFT
Detector chamber
C-foil window50g/cm2
beam dump
detector
shifted 30cm
new chamberfor GFM det.
Si strip detectors for the gas-filled mode operation
Junction sideJunction side
Matrix of 2 x 3 Si detectorsMatrix of 2 x 3 Si detectorsThickness Thickness ~~ 300 300 mmActive area = 5 x 5 cmActive area = 5 x 5 cm22, 16 resistive strips, 16 resistive strips
Ohmic sideOhmic side
3 mm3 mm
Electronics scheme
100100
PA
PA
PA
A
A
A
AD
C
Discr
Discr
Discr
Bit
Patt
ern
PA AD
C
A EnergyEnergy
X Pos. X Pos.
Y Pos. Y Pos.
CFD
TD
C
Beam referenceBeam reference
TriggerTriggerDelay = 100 nsDelay = 100 ns
Home made Electronics(PAs and shaping amplifiers)INFN NAPOLI
Summary and program
Test of electronics
Test of C-foil window with different gases
In beam test :
Pre-amplifiers: crosstalk
Preliminary tests with Si and α-source : signals OK
58Ni (200 MeV) + 197Au , PRISMA @ 60° : end of june
PRISMA in GFM : adequate Bρ up to masses A~200
Focal plane detector : 6 Si strips detectors 10 × 15 cm2
Aim : fusion reactions studies ; no super heavy elements
Under progress
Windows from GSI and LNL
Test of spot size, transmission, beam separation vs energy and gas…
Under progress
ANAMARI CodeANAMARI Code
0,0
5,0
10,0
15,0
20,0
0,0 0,2 0,4 0,6 0,8BQ
fwh
m (
cm)
40Ca+172Dy 1Torr
X
Y0
5
10
15
20
25
0 0,2 0,4 0,6 0,8
BQ
fwh
m (
cm)
32S+184W 1Torr
Y
X
•65cm•100cm•150cm•200cm
Section by section calculation using mid-section energy and <q> via 1st order transfer matrix Straggling added at the end of each section (assuming gaussian distribution ) Charge exchange not taken into account (ok if mean free path is short) Very fast
Without charge exchangeone cannot optimize the pressure one cannot estimate the background
being implemented
48Ca (200MeV) + 172Yb 216Th + 4n
1Torr He
216Th
48Ca
ANAMARI CodeANAMARI Code
The program assumes a full charge state equilibration. As we will see, it may not be appropriate
TRAJIG CodeTRAJIG Code
0,0
5,0
10,0
15,0
20,0
25,0
30,0
35,0
0,0 0,2 0,4 0,6 0,8 1,0
BQ(T)
fwh
m(c
m)
0,0
5,0
10,0
15,0
20,0
25,0
30,0
0,0 0,2 0,4 0,6 0,8 1,0
BQ(T)
fwh
m(c
m)
48Ca (200MeV) +172Yb 216Th + 4n
1Torr
36S (160MeV) +184W 216Th + 4n
1Torr
65cm100cm150cm200cm
X
Y
4th order Runge-Kutta trajectory calculations
Straggling added step by step, according to G.Amsel, G.Battistig, A.L’Hoir Nuc. Instr. Methods B201 (2003) 325
Charge exchange included. Cross sections from A.S.Schlachter et al. Phys.Rev. A11 (1983) 3372 assuming detailed balance and 1e exchange approximation.
Yields reasonable results from high vacuum to large pressures
above: first calculations without charge exchange
TRAJIG CodeTRAJIG Code
Approximations usedApproximations used: :
• schematic (ideal) optical elements (no fringing field)
• cross sections and charge distributions are calculated only once per section, at the average estimated energy.
The charge-exchange cross sections are estimated by
• single electron loss or capture approximation plus ...
• empirical adjustment in order to reproduce the assumed charge distribution
The most critical approximations are related to the charge-exchange
charge distribution: R.O.Sayer, Revue Phys. Appl. 12, 1977, 1543.
cross sections: A.S.Schlachter et al. Phys.Rev. A11 (1983) 3372
Trajig calculation for AuMeVNi 19758 )220( @60° 0° aperture gas: Helium
197Au
10-5 mb
10-4 mb
10-2 mb
0.1 mb
0.2 mb
0.5 mb
1 mb
2 mb
5 mb
10 mb
197Au
0
5
10
15
20
25
30
35
40
0,01 0,1 1 10
P(mbar)
fwh
m (
cm)
Trajig calculation for AuMeVNi 19758 )220( @60° 0° aperture gas: Helium
charge-exchange contribution
multiple scattering contribution
Trajig calculation for AuMeVNi 19758 )220( @60°
58Ni197Au
0° aperture
0.01mb
0.1mb
0.5mb
1 mb
2 mb
3 mb
5 mb
Trajig calculation for AuMeVNi 19758 )220( @60°
58Ni 197Au
3° aperture
0.01mb
0.1mb
0.5mb
1 mb
2 mb
3 mb
5 mb58Ni 197Au
Calculated 2D XY spectrumCalculated 2D XY spectrum
197Au58Ni
Focal plane detector
2 mbar of He
AuMeVNi 19758 )220( Prisma @ 60° 3° aperture
Trajig calculation AuMeVNi 19758 )220( @60° 0° aperture
0.01mb
0.1mb
0.5mb
1 mb
2 mb
3 mb
5 mb58Ni
197Au
gas: Argon
48Ca (200MeV) + 172Yb 216Ra + 2p2n
216Ra
172Yb
48Cano charge exchange2mb He
with charge exchange
A fusion example
2mb Ar
ER
48Ca
48Ca (200MeV) + 172Yb 216Ra + 2p2n
10mb He
ER
48Ca
other options
How does GFM Prisma compare? How does GFM Prisma compare?
Sep. Laboratory Configuration Main topic
RITU JYFL QDQQ HE spect. Z<103
GARIS RIKEN DQQD SHE prod. & chem.
DGFRS FLNR DQQ SHE production
BGS LBL QDD SHE prod. & chem.
TASCA GSI DQQ SHE prod. React. & Chem.
SHE spectr. Z>104
PRISMA LNL QD H.I. fusion reaction ?
• we cannot get into the SHE competition (accelerator and rigidity limitation) • we are ill equipped to compete in the HE spectroscopy (not with GFM) • a possibility is fusion reaction studies: it depends strongly on beam rejection, necessary to measure at low cross sections and reliability of the simulations.