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The present 35 keV line is shown in Figure 1 It consist of two solenoids, two current toroids, emittance probe and RF deflector. The RF defector proved not to be use full to chop the beam at this (35keV) due to neutralization REF 1. Now beam is chopped in 750 keV line and this chopper is not being used.
Figure 2 show the beam emittance mesured at station E1. These emittances were transported back to ion-source to find the initial conditions. Than theses initial conditions were used to simulate the ion trajectories in this line. A code had been written to trace the ion trajectories from ion-source to the RFQ. This code does not include the space charge effects because we believe that the beam is fully neutralized. Figure 3 shows the particles trajectories for this line. The mesured current on the first toriod (L1) was xx mA and at toroid 2 (L2) was xx mA. Therefore the transmission from L1 to L2 was ~80%.
To impove the transmission we considered the permanent magnet solenoid before the first solenoid but simulations showed that might not help. Further simulations showed that it will be quite helpful to bring the first solenoid as close as possible to ion-source and second solenoid to RFQ, and removr the chopper box. Figure 4 shows the particle trajectories through new short line.
On Nov 14, 1995 beam was send though this line and current mesured at L1
and L2 were 91 and 84 mA and ther transmission was 91%
which is much better than before.
Figure 5 shows beam current at L1, L2, and L3 as fuction of ion-source arc-current. The maximum currents at L1, L2, and L3 were 114, 98, and 80 mA respectively.
Figure 6 shwos the transmissions between L1&L2(T12), L2&L3 (T23) and L1&L3 (T13) as a function of the arc current. The tranmission T12 is nearly arc current indepnedent but T23 is highly corelated to acr current so does T13. The Maximum values for T12, T23, and T13 were 92, 88, and 80 % respectivly.
Figure 7 shows the beam cuurent at L1, L2, and L3 as a fuction od ion-source pressure. Data are in two groups because there were two ion-sources were involved. These data were taken over one month with differnt arc currents therefore it does not shows the correlation between pressure and the beam current which is shown in figure 8. Figure 8 shows the beam current at L1, L2, and transmission between them as function of ion-source pressure at arc current of 12 A. We believe this correlation is due to stripping of electrons from H-. The transmission between L1 and L2 can be increased if one can provide more pumping right at the ion-source extractor.
Figure 9 shows beam current at L1, L2, and L3 during month of Nov 1995. The Maximum current at L1, L2, and L3 are 114, 98, and 80 mA respectively.
Figure 10 shows the transmissions between L1&l2 (T12), L2&L3 (T23), and L1&L3 (T13). The maximum transmissions for T12, T23, and T13 are 92, 88, and 80%.
Figure 11 shows the transmission T12, T23, and T13 vs beam currents at L1. Transmission T12 remain approximately same up 100 mA of L1 current than it drops where as transmissions T23 whcich is tranmmission through the RFQ is decreases stealy with beam current at L1.
Figure 12 shows the beam current at L3 vs beam current at L2. This figure shows that RFQ transmmission approching to its limiting value to transmit the beam current for the given emittance.
Figure 13 shows the RFQ transmmission as a function of the input beam current. For Lower current (~70 mA) transmmission is about 88% and it desrease almost linearly with input current.
Figure 14 shows the transmmission T12 as function of beam current at L1. Transmmission is nearly currrent independent..