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LISE PRESENTATION

DESCRIPTION :

The doubly achromatic LISE spectrometer [1] installed at GANIL is operated since 1984 and is mainly dedicated to the study of exotic nuclei. Secondary beams can be obtained by the interaction of high energy heavy ions (E/A<95 Mev) with thick targets in the D3 room.

The LISE spectrometer consists in two dipole magnets D31 and D32 selecting at 0° nuclear reaction products according to A/Z combined with an achromatic degrader located in the intermediate focal plane in the D3 room, which operates a A3/Z2 selection. The secondary beam are sent to two experimental rooms called D4 and D6. In the latter case, a Wien filter can be used to operate a third selection according to the secondary beam velocity in order to increase its purity. The program LISE++ is used to calculate the yields of fragments transmitted in a LISE spectrometer. The various optical configurations commonly used in the software program can be downloaded here.

Overview of the LISE spectrometer and its equipment

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The LISE spectrometer can be operated in three distinct modes:

  1. The standard mode is called the "LISE3 mode": The production target is located in D3 and the experimental setups are mounted on the LISE line either in D4 or in D6. In this mode,  the primary beam usually impinges on the D3 target with an angle of 0°. However angles up to 3.5° can be used in order to produce polarized secondary beams. In this condition, the primary beam is stopped in the thick jaws located at the exit of the target chamber.
  2. The "LISE 2K mode": The D32 dipole is replaced by the D7P one to increase the angular acceptance and the maximum magnetic rigidity of the spectrometer (see table 2). In such a mode, the experimental setup is mounted in D4 on the LISE 2K line.
  3. The "FULIS mode": It is dedicated to fusion-evaporation reactions in a thin target mounted upstream the Wien filter used to separate the primary beam from the reaction products transmitted to D6.

Several detectors are available all along the LISE beam line to optimize the tunning of the spectrometer and its performances as well as to identify the nuclei of interest by means of position, time of flight, energy loss and residual energy. Some of these detectors are used by default in all experiments, they are called 'standard'. Others are used on users requests, such as CAVIAR, the zero degree detection, or the use of a Ge detector for identifying isomers.

  1. Standard detection systems consist in silicon detectors (energy-loss and residual energy) placed at the  D4 and D6 focal plane associated with a position sensitive device (galotte) placed in D4. They are used to tune the secondary beam and to identify the produced fragments.
  2. The CAVIAR [2] detector is a thin wire chamber that can be inserted at the intermediate focal plane, just before the achromatic degrader. It allows to determine the Brho values of the fragments on an event by event basis. The CAVIAR detector can be coupled with a PPAC which gives an accurate time of flight value of the ions passing through the dispersive focal plane. With this mode the full momentum acceptance of the spectrometer can be used, provided that the beam intensity is typically lower than 105 pps on the detector.
  3. A detection at 0° in D6 consists of using 2 CATS detectectors to achieve the tracking of the ions before a secondary target and to determine their time of flight relative to other detectors. Moreover a digitally-processed ionization chamber is used to determine the energy loss, and a plastic scintillator to provide a time of flight value and a residual energy of the ions.

 

Acceptance and magnetic rigidity in the LISE3 and LISE 2K modes

 LISE3LISE 2K

Angular

acceptance (msr)

13.5

Momentum

acceptance (%)

± 2.5± 2.5

Magnetic rigidity

(T.m)

D31 < 4.3

D32 < 3.26

DA1,2 < 3.86

D31 < 4.3

D71 < 4.48

 

Acceptance FULIS mode

 FULIS

Angular

acceptance (mrad)

X=Y=20mrad

Velocity

acceptance (%)

± 5

Refs:

[1] R. Anne and A.C. Mueller, NIM B70 (1992) 276

[2] L. Perrot et al., STATUS OF THE CAVIAR DETECTOR AT LISE-GANIL, 11th International Conference on HEAVY ION ACCELERATOR TECHNOLOGY, 07-12 June 2009, Venezia, Italy

Spectrometer

D3-D6



LISE PRESENTATION
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