A Quadrupole Beam Transport Experiment for Heavy Ions under Extreme Space Charge Conditions

A Cs ion-beam transport experiment is in progress to study beam behavior under extreme space charge conditions. A five-lens section matches the beam into a periodic electrostatic quadrupole FODO channel and its behavior is found to agree with predictions. With the available parameters (⩽200 keV, ⩽20 mA, πε
_n
⩾ 10
^-7
π rad-m, up to 41 periods) the transverse (betatron) oscillation frequency (γ) can be depressed down to one-tenth of its zero current value (γ
_o
), where γ
²
= γ
²
_o
- ω
²
_p
/2, and ω
_p
is the beam plasma frequency. The current can be controlled by adjustment of the gun and the emittance can be controlled independently by means of a set of charged grids.