The Booster accepts 30 MeV protons injected from the linear accelerator URAL-30 that yields beam pulses of 10 ms length. Their current is adjustable within a 30–70 mA range. Horizontal and vertical emittances of beam at exit from the URAL-30 are both equal to 40p mm

xmrad (at 95% level). Momentum spread of injected beam is ±3,0x10^-3.

Beam injection scheme

Beam injection into the Booster is accomplished with four pulsed magnets UBM1–UBM4 and septum magnet SM1. Intensity of the accelerated beam depends upon the injection scheme implemented. There are 1-, 2-, 3- and 4-turn injection schemes available by now. One-turn rotation period is 1,34 ms. During the multi-turn injection process, effective horizontal emittance of the accumulated beam increases to 40p cmx

mrad. Beam brightness can be tuned by varying both, average current from the URAL-30 and number of injection turns.

Acceleration

On injection, the beam is uniform and occupies the entire ring. Then, the beam is captured into a single RF bucket, and longitudinal size of the bunch shrinks with beam energy increasing. To this end, in a routine operation mode with 1.32 GeV top energy, the bunch would occupy 22% of the orbit circumference. It corresponds to bunch length of 80 ns and momentum spread of ±2,7x10^-3. By varying amplitude across RF accelerating cavities, one can lengthen the ejected bunch to about 160 ns with its momentum spread being reduced to Dр/р=±1,3x10^-3.

Beam ejection scheme

Beam ejection from the Booster is accomplished with the three bump magnets BM1-BM3, septum magnet SM2 and pulsed kicker magnet UM1. Trigger to fire UM1 is synchronized to phase of accelerating RF voltage so as to lock the 100 ns long front of the pulsed current to the beam gap.

Energy of ejected beam can be varied in a wide, 200–1320 MeV range. Feasible value of energy discreteness is dictated by accuracy available of magnetic field measurements throughout the acceleration cycle. The guide field is measured with a probe based on electron paramagnetic resonance effect and analog integrator able to resolve a 5 Gs field increment. Thus, the attainable fractional error of beam energy at extraction does not exceed 2,4x10^-3 at lower and 5,9x10^-4 at higher energies.

Given emittances of 20p mmxmrad horizontally and 10p mmxmrad vertically, beam spot size amounts to around ~4x

4 cm² upstream of the experimental zone. It can be varied through retuning the beam transfer line optics and depends on position of a sample to be irradiated. Position of the beam center can be steered with dipole corrector magnets.

Delicate operation options

There exists a possibility to run the Booster in optional modes that might be requested for a delicate applied study. Namely,

	By applying to shortened pulses that power injection bump magnets in a 1-turn injection scheme, one can accumulate and accelerate up to 3,0x1011 protons per a cycle. Adding the second RF harmonic to the accelerating field may be used to decrease momentum spread of the beam, say, to ±5,0x10-4 at energy 1.32 GeV.
	Beam ejection with longitudinal emittances as small as 0.1–0.45 eVs is feasible. It can be achieved, at the expense of an increased beam loss, via imposing the RF voltage program with lower amplitudes throughout the cycle.

To improve accuracy of beam parameter diagnostics, beam extraction procedure can be accompanied by issuing a protocol containing rotation frequency and beam orbit data, both measured at 10-20 ms prior to kick-out. Thus, beam energy can be monitored with an accuracy better than 10^-3.