Author: Cai, Y.
Paper Title Page
TUPFI016 Optimization of Triplet Quadrupoles Field Quality for the LHC High Luminosity Lattice at Collision Energy 1364
 
  • Y. Nosochkov, Y. Cai, M.-H. Wang
    SLAC, Menlo Park, California, USA
  • R. De Maria, S.D. Fartoukh, M. Giovannozzi, E. McIntosh
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404; and by the US DOE contract DE-AC02-76SF00515.
For the high lu­mi­nos­ity up­grade of the LHC (HL-LHC), the beta func­tions at two in­ter­ac­tion points (IP) will be sig­nif­i­cantly re­duced com­pared to the nom­i­nal LHC lat­tice. This will re­sult in much higher peak beta func­tions in the inner triplet (IT) quadrupoles ad­ja­cent to these IPs. The con­se­quences are a larger beam size in these quadrupoles, higher IT chro­matic­ity, and stronger ef­fects of the IT field er­rors on dy­namic aper­ture (DA). The IT chro­matic­ity will be com­pen­sated using the Achro­matic Tele­scopic Squeez­ing scheme*. The in­creased IT beam size will be ac­com­mo­dated by in­stalling large aper­ture Nb3Sn su­per­con­duct­ing quadrupoles with 150 mm coil di­am­e­ter. The field error tol­er­ances in these mag­nets must sat­isfy the re­quired ac­cept­able DA while being rea­son­ably close to re­al­is­ti­cally achiev­able field qual­ity. Eval­u­a­tion of the IT field er­rors was per­formed for the LHC up­grade lay­out ver­sion SL­HCV3.01 with IT gra­di­ent of 123 T/m and IP col­li­sion beta func­tions of 15 cm in both planes. Dy­namic aper­ture cal­cu­la­tions were per­formed using Six­Track. De­tails of the op­ti­miza­tion of the IT field er­rors are pre­sented along with cor­rec­tions to achieve the field qual­ity spec­i­fi­ca­tions.
* S. Fartoukh, “An Achromatic Telescopic Squeezing (ATS) Scheme for LHC Upgrade’’, in proceedings of IPAC11, p. 2088. 		 
 
TUPFI017 Evaluation of Field Quality for Separation Dipoles and Matching Section Quadrupoles for the LHC High Luminosity Lattice at Collision Energy 1367
 
  • Y. Nosochkov, Y. Cai, M.-H. Wang
    SLAC, Menlo Park, California, USA
  • R. De Maria, S.D. Fartoukh, M. Giovannozzi, E. McIntosh
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404; and by the US DOE contract DE-AC02-76SF00515.
The high lu­mi­nos­ity up­grade of the LHC (HL-LHC) lat­tice re­quires new larger aper­ture mag­nets to be in­stalled in the low-beta in­ter­ac­tion re­gions (IRs). These in­clude Nb3Sn su­per­con­duct­ing (SC) triplet quadrupoles, Nb-Ti SC sep­a­ra­tion dipoles D1 and D2, and SC Q4 quadrupoles. The up­grade sig­nif­i­cantly re­duces the beta func­tions at these IRs, pro­duc­ing higher beta func­tions and larger beam size in these mag­nets, and re­quir­ing a larger aper­ture. The high beta func­tions also in­crease the im­pact of high order field er­rors in these new mag­nets on dy­namic aper­ture (DA). There­fore, to main­tain an ac­cept­able DA, new spec­i­fi­ca­tions for the mag­net field qual­ity are re­quired. Since the IR error ef­fects at col­li­sion are dom­i­nated by the triplets, their field qual­ity has been stud­ied and spec­i­fied first*. As a next step, the field er­rors were added to the D1 and D2 dipoles and Q4 quadrupoles while main­tain­ing the triplet er­rors to spec­i­fi­ca­tions. The im­pact of the er­rors on DA has been de­ter­mined in long term track­ing sim­u­la­tions using Six­Track. The op­ti­mized field error spec­i­fi­ca­tions for the D1, D2 and Q4 mag­nets are pre­sented.
* Y. Nosochkov, Y. Cai, M-H. Wang, S. Fartoukh, M. Giovannozzi, R. de Maria, E. McIntosh, “Optimization of Triplet Field Quality for the LHC High Luminosity Lattice at Collision Energy”, IPAC 2013. 		 
 
WEPWA075 High-gain X-ray FELs using a Transverse Gradient Undulator in an Ultimate Storage Ring 2286
 
  • Y.T. Ding, P. Baxevanis, Y. Cai, Z. Huang, R.D. Ruth
    SLAC, Menlo Park, California, USA
  
  An “ul­ti­mate” stor­age ring based on PEP tun­nel has been de­signed to achieve dif­frac­tion lim­ited emit­tance (at 1.5 Angstrom)[*]. With suf­fi­cient peak cur­rent, the beam bright­ness of such an “ul­ti­mate” stor­age ring may be suf­fi­cient to drive a short-wave­length, high-gain FEL. How­ever, the large en­ergy spread in­trin­sic to stor­age rings hin­ders the FEL ap­pli­ca­tions for x-ray wave­lengths. To over­come this prob­lem, we adopt the trans­verse-gra­di­ent un­du­la­tor con­cept[**][***] to study a high-gain FEL in an ul­ti­mate stor­age ring. Using PEP-X as an ex­am­ple, we showed from sim­u­la­tions that a high-gain FEL at the pho­ton en­ergy 1keV with a peak power of a few hun­dred megawatts can be achieved within a sat­u­ra­tion length of 100 me­ters.
* Y. Cai et al., Phys. Rev. ST Accel. Beams 15, 054002 (2012).
** T. Smith et al., J. Appl. Phys. 50, 4580 (1979)
*** Z. Huang, Y. Ding and C. B. Schroeder, Phys. Rev. Lett 109, 204801 (2012).