Double shot operation of the ejection system for bubble chambers at the IHEP accelerator

The paper presents a description of double shot proton ejection onto the external target, worked out for exposure of bubble chambers Mirabelle and Ludmila, whose minimum time interval between consequent expansions is about 1 sec. Ejection of protons with maximum energy is realized at the flat top of the magnetic cycle. The first ejection is realized at the beginning of the flat top with a bunched beam, the second one at the end of the flat top with a debunched beam remaining after interaction with the internal targets. Intensity in the first shot is determined by the choice of the number of the accelerated proton beam ejected bunches. Intensity in the second shot is kept at a required level by a special device with an accuracy not worse than +- 10%. The time interval between the shots is 1.5-2 sec in this case. The equipment designed and modified for this purpose has been described. The results on studying optical characteristics of the beam are presented. The results of bubble chamber Ludmila exposures show that the worked out system may be successfully used for double shot exposure of bubble chambers