Beam transport physics issues for the recirculating linear accelerator
The Recirculating Linear Accelerator (RLA) utilizes the Ion Focused Regime (IFR) of beam transport plus a ramped bending field to guide the beam around the curved sections. Several issues of beam transport are considered. Beam transverse perturbations that could result in growth of the ion hose instability are analyzed. It is found that transverse kicks due to bending field errors, energy mismatches and fringe fields are the most important. The scaling of these perturbations with beam and channel parameters is derived. The effect of ramping of the bending field on the preformed plasma channel is then considered. For RLA experimental parameters the effect is found to be very small. For high energies however, in addition to axial heating, it is found that ramping the field causes compression of the plasma channel along the radius of curvature. This compression results in a quasi-equilibrium plasma electron temperature along the field lines which leads to collisionless transport towards the walls. The analysis of compression is done in an approximate way using a single particle picture and the channel expansion is analyzed using an envelope solution which gives a simple expression for the expansion time. This solution is then verified by Buckshot simulations. For a bending field of 2 kG ramped in 2 [mu]-secs and an argon channel (RLA parameters) we estimate that the channel radius doubling time (along field lines) is of the order of 0.5 [mu]-secs. Finally the effect of electron impact ionization due to axially heated electrons by the action of the inductive field is estimated. It is found that in Argon gas the electron avalanche time could be as low as 0.5 [mu]-sec which is smaller than the field ramp time.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6914968
- Report Number(s):
- SAND-92-1841; ON: DE93004022
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
430200 -- Particle Accelerators-- Beam Dynamics
Field Calculations
& Ion Optics
430303* -- Particle Accelerators-- Experimental Facilities & Equipment
ACCELERATORS
BEAM EMITTANCE
BEAM FOCUSING MAGNETS
BEAM TRANSPORT
BEAMS
COLLISIONS
COMPUTERIZED SIMULATION
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ELECTRON COLLISIONS
EQUIPMENT
HOSE INSTABILITY
INSTABILITY
IONIZATION
LEPTON BEAMS
LINEAR ACCELERATORS
MAGNETIC FIELDS
MAGNETS
ORBITS
PARTICLE BEAMS
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
SIMULATION