• H. Geng, Y.T. Ding, Z. Huang
  SLAC, Menlo Park, California
• R. Bartolini
  Diamond, Oxfordshire
• D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The crossed-pla­nar un­du­la­tor is a promis­ing scheme for full po­lar­iza­tion con­trol in an x-ray FEL*. For SASE FELs, it has been shown a max­i­mum de­gree of cir­cu­lar po­lar­iza­tion of about 80% is achiev­able**. In this paper, we study the ef­fec­tive­ness of a cross un­du­la­tor for a seed­ed x-ray FEL. The de­gree of cir­cu­lar po­lar­iza­tion for both the fun­da­men­tal and the har­mon­ic ra­di­a­tion are con­sid­ered.

* K.-J. Kim, Nucl. Instrum. Methods A445, 329 (2000).
** Y. Ding, Z. Huang, Phys. Rev. ST-AB 11, 030702 (2008).

• R. Bartolini, C. Christou, J.H. Han, I.P.S. Martin, J. Rowland
  Diamond, Oxfordshire
• D. Angal-Kalinin, D.J. Dunning, F. Jackson, B.D. Muratori, N. Thompson, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

We pre­sent the progress with the de­sign of the 2.25 GeV su­per­con­duct­ing linac for the NLS pro­ject. We dis­cuss the per­for­mance achieved, the op­ti­mi­sa­tion strate­gies, the rel­e­vance of mi­crobunch­ing in­sta­bil­i­ty and the anal­y­sis of the ef­fect of var­i­ous jit­ter sources

• R. Bartolini, G. Rehm, J. Rowland
  Diamond, Oxfordshire
• P. Kuske
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
• I.P.S. Martin
  JAI, Oxford
• F. Schmidt
  CERN, Geneva

The cor­rect im­ple­men­ta­tion of the non­lin­ear ring model is cru­cial to achieve the top per­for­mance of a syn­chrotron light source. Sev­er­al dy­nam­ics quan­ti­ties can be used to com­pare the real ma­chine with the model and even­tu­al­ly to cor­rect the ac­cel­er­a­tor. Most of these meth­ods are based on the anal­y­sis of turn-by-turn data of ex­cit­ed be­ta­tron os­cil­la­tions. We pre­sent the ex­per­i­men­tal re­sults of the cam­paign of mea­sure­ments car­ried out at the Di­a­mond. A com­bi­na­tion of Fre­quen­cy Map Anal­y­sis and res­o­nant driv­ing terms mea­sure­ments has al­lowed a pre­cise cal­i­bra­tion of the non­lin­ear model ca­pa­ble of re­pro­duc­ing and then cor­rect­ing the non­lin­ear beam dy­nam­ics in the stor­age ring.

• C.A. Thomas, G. Rehm
  Diamond, Oxfordshire
• S.I. Bajlekov
  University of Oxford, Clarendon Laboratory, Oxford
• R. Bartolini, N. Delerue
  JAI, Oxford

Sin­gle shot emit­tance mea­sure­ment is es­sen­tial to as­sess the per­for­mance of new gen­er­a­tion light sources such as linac based X-ray FELs or laser plas­ma wake­field ac­cel­er­a­tors. To this aim, we have de­vel­oped a sin­gle shot emit­tance mea­sure­ment using at least 3 screens in­sert­ed in the beam at the same time, mea­sur­ing the beam size at dif­fer­ent po­si­tions in a drift space in one shot. We pre­sent here test mea­sure­ments per­formed at Di­a­mond in the trans­fer line from the Boost­er to the Stor­age Ring, using thin OTR and also YAG screens. We also com­pare these mea­sure­ments with re­sults from the more con­ven­tion­al quadrupole scan method and also mea­sure­ments using an OTR screen and an as­sem­bly of two cam­eras imag­ing the beam size and the beam di­ver­gence at a point near the waist of the beam. The va­lid­i­ty and lim­its of the new method are dis­cussed in the paper.

• P.H. Williams, D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, J.K. Jones, P.H. Williams
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford
• J. Rowland
  Diamond, Oxfordshire

We pre­sent progress in the de­sign of the re­cir­cu­lat­ing linac op­tion for the UK New Light Source. Im­prove­ments in all ac­cel­er­a­tor sec­tions have been made such that the out­put meets the re­quired spec­i­fi­ca­tions to drive the seed­ed NLS FELs. Full start-to-end sim­u­la­tions and tol­er­ance stud­ies are pre­sent­ed to­geth­er with a com­par­i­son to the base­line, sin­gle pass linac de­sign.

• D. Angal-Kalinin, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, F. Jackson, S.P. Jamison, J.K. Jones, B.D. Muratori, N. Thompson
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The de­sign of free elec­tron laser (FEL) driv­er needs care­ful beam trans­port de­sign to pass very short bunch­es through the switch­yard/spread­er to switch the beam to dif­fer­ent FEL lines. The spread­er de­sign which al­lows flex­i­bil­i­ty in op­er­a­tion has been adapt­ed fol­low­ing the LBNL de­sign*. In order to mea­sure the slice prop­er­ties of the bunch­es two beam di­ag­nos­tics lines are pro­posed, a straight one for beam com­mis­sion­ing pur­pos­es and a branch of the spread­er sim­i­lar to the FEL lines to mea­sure the ad­verse ef­fects that may arise due to pass­ing the short bunch­es through the kick­er and sep­tum mag­nets. As a part of ma­chine pro­tec­tion, post linac col­li­ma­tion sys­tem col­li­mates the halo par­ti­cles in trans­verse and en­er­gy planes. The de­sign of the col­li­ma­tion, beam spread­er and beam di­ag­nos­tics lines is dis­cussed.

* Zholents A.A. et al, CBP Tech Note 401, 2009

• J. Rowland, R.T. Fielder
  Diamond, Oxfordshire
• R. Bartolini
  JAI, Oxford
• R. Nagaoka
  SOLEIL, Gif-sur-Yvette

With­in the com­mon pro­gramme on the anal­y­sis of col­lec­tive in­sta­bil­i­ties at Di­a­mond and SOLEIL, the nu­mer­i­cal codes mb­track and sb­track have been ex­tend­ed to in­clude a full de­scrip­tion of the non­lin­ear­i­ties in the stor­age rings by means of the non­lin­ear one-turn map. We pre­sent the de­tails of the map im­ple­men­ta­tion and the re­cent re­sults on the anal­y­sis of the ef­fects of the non­lin­ear terms of the map on the char­ac­ter­is­tics of the col­lec­tive in­sta­bil­i­ties at the two ma­chines.

• D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• R. Bartolini
  JAI, Oxford
• H. Geng, Z. Huang
  SLAC, Menlo Park, California
• B.W.J. McNeil
  USTRAT/SUPA, Glasgow

Op­ti­mi­sa­tion stud­ies of an HHG-seed­ed har­mon­ic cas­cade FEL de­sign for the UK's pro­posed New Light Source (NLS) fa­cil­i­ty are pre­sent­ed. Three sep­a­rate FELs are planned to meet the re­quire­ments for con­tin­u­ous cov­er­age of the pho­ton en­er­gy range 50-1000 eV with vari­able po­lar­i­sa­tion, 20 fs pulse widths and good tem­po­ral co­her­ence. The de­sign uses an HHG seed source tune­able from 50-100 eV to pro­vide di­rect FEL seed­ing in this range, and one or two stage har­mon­ic cas­cades to reach the high­er pho­ton en­er­gies. Stud­ies have been car­ried out to op­ti­mise a har­mon­ic cas­cade FEL op­er­at­ing at 1 keV; top­ics in­ves­ti­gat­ed in­clude mod­u­la­tor con­fig­u­ra­tion, seed power level and ef­fects of the HHG seed struc­ture. FEL sim­u­la­tions using re­al­is­tic elec­tron beam dis­tri­bu­tions are pre­sent­ed and tol­er­ance to in­creased emit­tance has been con­sid­ered.

• I.P.S. Martin
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford
• D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The New Light Source pro­ject aims to con­struct a suite of seed­ed free-elec­tron lasers driv­en by a 2.25GeV cw super con­duct­ing linac. As part of the up­grade path, a num­ber of op­tions are being con­sid­ered for gen­er­at­ing ultra short (<1fs) soft x-ray puls­es, with low-charge 'sin­gle-spike' op­er­a­tion and bunch slic­ing like ap­proach­es of par­tic­u­lar in­ter­est, in­clud­ing as a pos­si­ble ex­ten­sion to echo-en­hanced har­mon­ic gen­er­a­tion. In this paper we pre­sent the sta­tus of this work, in­clud­ing re­cent re­sults from fully start to end sim­u­la­tions.

• A. Kling, K. Balewski
  DESY, Hamburg
• R. Bartolini
  JAI, Oxford

PETRA III is a 3rd gen­er­a­tion syn­chrotron ra­di­a­tion light source which start­ed com­mis­sion­ing in April 2009. Turn-by-turn ca­pa­bil­i­ties are avail­able for all 227 BPMs in­stalled in the stor­age ring thus pro­vid­ing a pow­er­ful di­ag­nos­tic tool for the char­ac­ter­i­za­tion of the lin­ear and non­lin­ear mo­tion of the stored beam. We re­port on first re­sults of beam dy­nam­ics stud­ies using mul­ti­turn data ac­quired at PETRA III and first steps to­wards a cal­i­bra­tion of the lin­ear and non­lin­ear lat­tice model of the stor­age ring.

• I.P.S. Martin, G. Rehm, J. Rowland, C.A. Thomas
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The Di­a­mond stor­age ring has been op­er­at­ed in low alpha mode pro­vid­ing short-pulse ra­di­a­tion for pump-probe ex­per­i­ments and co­her­ent ra­di­a­tion for THz/IR mea­sure­ments. Two lat­tices have been im­ple­ment­ed, with both ca­pa­ble of pro­vid­ing a vari­able alpha in the range ±2x10^-5, down to min­i­mum val­ues well below 1x10^-6. The sec­ond lat­tice ad­di­tion­al­ly pro­vides a low emit­tance of 4nm.​rad, com­pared to 35nm.​rad for the first lat­tice. An overview of op­er­a­tion in low alpha mode is given, along with first mea­sure­ments of co­her­ent emis­sion at long wave­lengths under a va­ri­ety of con­di­tions.

• B. Singh, R.T. Fielder, J. Rowland
  Diamond, Oxfordshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

Di­a­mond op­er­ates with 10 in-vac­u­um in­ser­tion de­vices at 5 mm gap, two Ap­ple-II, two su­per­con­duct­ing and two nor­mal con­duct­ing wig­glers. We re­port here the cor­rec­tion of the lin­ear op­tics of wig­glers and mea­sure­ments of non­lin­ear ef­fects such as dy­nam­ic aper­ture and fre­quen­cy maps and their im­pacts on in­jec­tion ef­fi­cien­cy, life­time and loss dis­tri­bu­tion in op­er­a­tion of the stor­age ring.