Meeting on Linac4 - PSB BI Line, 26-January-2009

Present:  Masamitsu Aiba; Jan Borburgh; Christian Carli; Tony Fowler; Michael Hourican; Volker Mertens; Luc Sermeus; Wim Weterings

Excused:  Brennan Goddard

• WW reported on the outcome of L4 PSB injection review and the following issues were highlighted:

  • Locating the chicane magnets outside of the (conductive) beam pipe is unique, and possible effects on the field quality should be carefully evaluated. Also the quality requirements for the chicane magnets, both uniformity and higher harmonics, including the effects of eddy currents in the beam pipes should be studied. Specifications should be made as to the field quality required by the chicane magnets, in terms of allowed closed orbit distortion and tune shift, and this should inform the design of the magnets and power supplies. It is recommended to pPower the chicane magnets in series if possible, since most existing systems use single power supplies to insure field matching.
  • The proposed longitudinal painting scheme is extremely complex, considering the rather marginal benefit.
  • The loss on the head and tail dumps within the septum is significant, and the resulting activation will likely make the system unserviceable. Considering the beam load on the head and tail dumps, methods of minimizing the head and tail should be investigated.
  • The load on the stripping foil is lower than elsewhere, and the foil is more likely to be damaged mechanically, than by beam. An electron collector will not needed.
  • Instrumentation at the injection region is extremely important.
  • Besides linear painting, other wave forms should be considered.

• For information, additional comments to the outcome of the L4 PSB injection review were given by Karlheinz Schindl.
   
• WW further presented 2 proposals (with the impact on other equipment) to solve the issues related to the Head Dump:

  1. Use a combination of Kicker and Septum magnets instead if the 'switching magnet' LTB.BHZ40 to defect the head (and tail) into the dump of the measurement lines. This system could also be used to deflect the full beam to the measurement lines.
  2. Add a SMV on top of SMV1 to deflect the head of the pulse to a dump located outside the BISMV tank and BI  line
  . This would also require an increase of the beam offset at BI.DIS from 5.2 mm to 5.5 mm, the BI.DIS4 deflection from 3.62 mrad to 4.3 mrad and the BI.DVT40 deflection from 7.27 to 8 mrad.

  It was decided that a price estimate of both solutions should be made in order to forward these proposals to the L4 management.
   
• JB presented results of 2D simulations made by BB of a possible 2 turn BS1 RBEND CF magnet. These simulations confirmed that a gradient of 0.03T/m can be obtained in the centre of the magnet. However at the edges, closer to the conductors, the gradient is not constant. The deviation that can be tolerated should be specified by the accelerator physicists (BG? CC? MA?). The 3D simulations showed that the two turn versionfor a 400mm long magnet yields only magnetic length of 365mm.  JB mentioned that for the RBEND presented in a  previous presentation it the non-linearity of the B.dl/I was less tan 5e-4. However, the error on this value is dominated by the finite element mesh and BH curve used: 1e-3 at best.
   

WW