The NSCL cyclotron gas stopper – Entering commissioning

Abstract

Linear gas stopping cells have been used successfully at NSCL to slow down ions produced by projectile fragmentation from the 100 MeV/u to the keV energy range. These 'stopped beams' have first been used for low-energy high precision experiments and more recently for NSCLs re-accelerator ReA.A gas-filled reverse cyclotron is currently under construction by the NSCL to complement the existing stopping cells: Due to its extended stopping length, efficient stopping and fast extraction is expected even for light and mediummass ions, which are difficult to thermalize in linear gas cells. The device is based on a 2.6 T maximum-field cyclotron-type magnet to confine the injected beam while it is slowed down in ≈100 mbar of LN 2 -temperature helium gas.Once thermalized, the beam will be transported to the center of the device by a traveling-wave RF-carpet system, extracted along the symmetry axis with an ion conveyor and miniature RF-carpets, and accelerated to a few tens of keV of energy for delivery to the users.The superconducting magnet has been constructed on a 60kV platform and energized to its nominal field strength. The magnet's two cryostats use 3 cryo-refrigerators each and liquid-nitrogen cooled thermal shields to cool the coil pair to superconductivity. This concept, chosen not to have to rely on external liquid helium, has been working well. Measurements of axial and radial field profiles confirm the field calculations. The individual RF-ion guiding components for low-energy ion transport through the device have been tested successfully. The beam stopping chamber with its 0.9 mdiameter RF carpet system and the ion extraction system are being prepared for installation inside the magnet for low-energy ion transport tests.

Current Status of r-Process Nucleosynthesis

“…This process avoids any chemistry constraints on the beam and is able to produce exotic beams from a variety of primary beams. The LEBIT facility operates a linear gas stopper and a cyclotron gas stopper [135] along with a laser ablation ion source and a plasma ion source, both used for stable beams. An accumulator and buncher downstream of the gas stoppers and ion sources cools the beam prior to injection into the single Penning trap system [136].…”

Proposal of a New Double-Nozzle Technique for In-Gas-Jet Laser Resonance Ionization Spectroscopy

“…Near the extraction nozzle having the small throat diameter, ions are extracted out of the gas cell into vacuum conditions by supersonic buffer gas jet. Description of various gas cell apparatus readers can find elsewhere, for example, in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and links within them.…”

Proposal of a New Double-Nozzle Technique for In-Gas-Jet Laser Resonance Ionization Spectroscopy

“…Near the extraction nozzle with a small throat diameter, ions are extracted from the gas cell into vacuum conditions by a supersonic buffer gas jet. Description of various gas cell apparatus readers can find elsewhere, for example, in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and links within them.…”