Test of PRISMA in Gas Filled Mode B.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 (2002) : 60 Ni+ 89 Y C.L. Jiang et al., Phys. Rev. Lett (2004) : 64 Ni+ 64 Ni Example: the hindrance phenomenon

Principles of operation of a gas-filled magnetic spectrometer Charge states merge 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 58 Ni 112 Sn 148 Sm 176 Hf 208 Pb 252Fm 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 Prisma max. rigidity for central trajectory

Magnetic rigidity of Evaporation Residues Projectile and ER rigidity as a function of the target E=V B for all practical cases Forget reverse kinematics! S Ni Ca Se 1.5Tm projectile CN

3230 mm 800 mm 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: 4 He is the most popular but other gases should be tested detector C-foil window Gate valve Gas filling

EFB 1.2Tm The setup for the GFM operation of Prisma Prisma at 0° 1.5Tm DRIFT Detector chamber C-foil window 50  g/cm 2 beam dump detector shifted 30cm

new chamber for GFM det.

Si strip detectors for the gas-filled mode operation Junction side Matrix of 2 x 3 Si detectors Thickness ~ 300  m Active area = 5 x 5 cm 2, 16 resistive strips Ohmic side 3 mm

Electronics scheme 100  PA A A A ADC Discr Bit Pattern PA ADC A Energy X Pos. Y Pos. CFD TDC Beam reference Trigger Delay = 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 58 Ni (200 MeV) Au, 60° : end of june PRISMA in GFM : adequate Bρ up to masses A~200 Focal plane detector : 6 Si strips detectors  10 × 15 cm 2 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 Code 40 Ca+ 172 Dy 1Torr X Y 32 S+ 184 W 1Torr Y X 65cm 100cm 150cm 200cm  Section by section calculation using mid-section energy and  via 1 st 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 exchange one cannot optimize the pressure one cannot estimate the background being implemented

48 Ca (200MeV) Yb  216 Th + 4n 1Torr He 216 Th 48 Ca ANAMARI Code The program assumes a full charge state equilibration. As we will see, it may not be appropriate

TRAJIG Code 48 Ca (200MeV) Yb  216 Th + 4n 1Torr 36 S (160MeV) W  216 Th + 4n 1Torr  65cm  100cm  150cm  200cm X Y  4 th 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 Code Approximations 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, cross sections: A.S.Schlachter et al. Phys.Rev. A11 (1983) 3372

Trajig calculation 0° aperture gas: Helium 197 Au mb mb mb 0.1 mb 0.2 mb 0.5 mb 1 mb 2 mb 5 mb 10 mb 197 Au

Trajig calculation 0° aperture gas: Helium charge-exchange contribution multiple scattering contribution

Trajig calculation 58 Ni 197 Au 0° aperture 0.01mb 0.1mb 0.5mb 1 mb 2 mb 3 mb 5 mb

Trajig calculation 58 Ni 197 Au 3° aperture 0.01mb 0.1mb 0.5mb 1 mb 2 mb 3 mb 5 mb 58 Ni 197 Au

Calculated 2D XY spectrum 197 Au 58 Ni Focal plane detector 2 mbar of He 60° 3° aperture

Trajig 0° aperture 0.01mb 0.1mb 0.5mb 1 mb 2 mb 3 mb 5 mb 58 Ni 197 Au gas: Argon

48 Ca (200MeV) Yb  216 Ra + 2p2n 216 Ra 172 Yb 48 Ca no charge exchange 2mb He with charge exchange A fusion example

2mb Ar ER 48 Ca 48 Ca (200MeV) Yb  216 Ra + 2p2n 10mb He ER 48 Ca other options

How does GFM Prisma compare? Sep.LaboratoryConfigurationMain topic RITUJYFLQDQQHE spect. Z<103 GARISRIKENDQQDSHE prod. & chem. DGFRSFLNRDQQSHE production BGSLBLQDDSHE prod. & chem. TASCAGSIDQQSHE prod. React. & Chem. SHE spectr. Z>104 PRISMALNLQDH.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.