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Monday, August 05

BECOLA Facility at NSCL/MSU:
Collinear Laser Spectroscopy with Bunched Beams

K. Minamisono, National Superconducting Cyclotron Lab,
Michigan State University, East Lansing
ORNL, Physics Division Seminar
3:00 PM — 4:00 PM, Building 6008, Large Conference Room
Contact: Alfredo Galindo-Uribarri (, 865.574.6124


The BEam COoler and LAser spectroscopy (BECOLA) facility [1] has been installed and currently commissioned at National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. BECOLA will be used to perform both laser hyperfine structure measurements and atomic/nuclear spin manipulation using optical pumping and nuclear-magnetic resonance techniques for rare isotopes at low counting rates. BECOLA was designed to accept low-energy (< 60 keV) beams from the NSCL gas stopping stations and also from the future Facility for Rare Isotope Beams (FRIB) [2] without any modification to the system. Charge radii and nuclear moments of light transition metals will be initially targeted [3], which are difficult to produce at other facilities.

There are three major components to BECOLA; the cryogenic beam cooler and buncher, the collinear laser spectroscopy system, and an offline ion source. The cooler/buncher reduces the emittance of the incoming beams and provides short ion bunches to increase the detection sensitivity of the laser-induced fluorescence measurements and greatly facilitate studies of radioactive ions produced at low rates [4]. The laser system consists of continuous-wave Ti:S and dye ring laser and a frequency doubler. A charge-exchange cell (CEC) was used for experiments that require atomic (neutral) beams by neutralizing ion beams via charge-exchange reactions with an alkali vapor. Resonant fluorescence was collected using an ellipsoidal reflector and detected by a photomultiplier tube. The CEC for neutral beams or the ellipsoidal reflector of the photon detection system for ion beams were operated on a variable potential to change the incoming ion-beam velocity, to tune the Doppler-shifted laser frequency into resonance with the hyperfine transition of interest [5]. The detected fluorescence was recorded as a function of the scanning voltage. A Penning ion gauge (PIG) ion source [6] is being constructed for BECOLA experiments to produce stable isotopes of transition metals. The PIG ion source is a critical component of the BECOLA facility to perform system calibration during online experiments as well as offline developments for possible laser transition schemes.

Results of the first online experiment scheduled this summer as well as the science program and the overall performance characteristics of the laser spectroscopy system with bunched beams will be presented.

This work was supported in part by the NSF grant PHY-1102511.

[3] K. Minamisono, et al., Proc. Insti. Nucl. Theory 16, 180 (2009).
[4] A. Nieminen et al., Phys. Rev. Lett. 88, 094801 (2002).
[5] S. L. Kaufman, Opt. Comm. 17, 309 (1976).
[6] Z. Nouri et al., Nucl. Instrum. Methods Phys. Res. A 614, 174 (2010).