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The LIRAT facility

 The LIRAT low-energy beam facility at SPIRAL




   The LIRAT acronym stands for "Ligne d'Ions Radioactifs A Très basse énergie". The implementation of a low-energy beam facility at SPIRAL was proposed in 1998  by G. Auger, B. Blank and C. Lebrun [1] with the aim to perform nuclear structure, fundamental interaction and solid state physics studies with the radioactive ion beams delivered by the SPIRAL target ion source system. The construction of the beam line started in 2001 with A. Peghaire as a project leader and a first radioactive beam of 19Ne1+ was delivered in 2005.


The LIRAT line

   The LIRAT line consists in a 45° dipole and in a set of magnetic quadrupoles and stearers driving with a efficiency better than 80 % 80 pi mm.mrad beams of less than 30 keV (See figure 1). The Brho  is limited to 0.136 T.m, which allows to transport A < 89 ions in a single charge state. The optics was design in order to obtain a beam spot size of about 5 mm at the focal point.


   At present, only 4 of the radioactive ion beams produced by the SPIRAL TIS can be used at the LIRAT facility . They are listed in table 1 where only the charge states associated with the largest intensities are considered. (see the SPIRAL beam web page for more details).


   All SPIRAL beams should become available by 2011. Within the SPIRAL2 project, the LIRAT line should transport the SPIRAL beams to the DESIR facility.



Figure 1: The LIRAT line at SPIRAL


Table 1: Available beams at LIRAT

IonqI (pps)
 6He 1+ 2.1x08
 19Ne 2+ 1.5x108
 32Ar 9+


 35Ar 8+


Physics program at LIRAT

    Since 2005, the LIRAT line is used to deliver the intense (I > 108 pps) 6He1+ SPIRAL beam to the LPCTrap setup consisting in a RFQ cooler-buncher and in a transparent Paul Trap [2]  (see figure 2).

The setup is devoted to the measurement of the beta-neutrino angular correlation parameter a in the pure Gamow-Teller ß decay of 6He. The aim of the experimental campain is to search for tensor type  contributions to the weak interaction by means of a precise measurement of the angle between the emitted ß particles and the recoiling 6Li2+ ions.

Two runs performed in 2006 and in 2008  allowed to determine the angular correlation parameter with a statistical incertainly of 1.8 % [3]. Systematics effects retaled to the trapping technique are under investigation.


Figure 2: The LPCTrap setup at LIRAT.


Details about the experimental setup and the first achievements can be found here.


Contact: J.-C. Thomas


[1] G. Auger, B. Blank and C. Lebrun, GANIL Scientific Committee, 1998.

[2] D. Rodriguez et al., Nucl. Instr. Meth. Phys. Res. A565, 876 (2006).

[3] X. Fléchard et al., Phys. Rev. Lett. 101, 212504 (2008).



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