• W.J. Corbett, A.S. Fisher, X. Huang, J.A. Safranek, S. Westerman
  SLAC, Menlo Park, California
• W.X. Cheng
  BNL, Upton, Long Island, New York
• W.Y. Mok
  Life Imaging Technology, Palo Alto, California

As SPEAR3 moves clos­er to trick­le-charge topup in­jec­tion, the com­plex phase-space dy­nam­ics of the in­ject­ed beam be­comes in­creas­ing­ly im­por­tant for cap­ture ef­fi­cien­cy and ma­chine pro­tec­tion. In the hor­i­zon­tal plane the beam ex­e­cutes ~12mm be­ta­tron os­cil­la­tions and be­gins to fil­a­ment with­in 10's of turns. In the ver­ti­cal plane the beam is more sta­ble but a pre­mi­um is placed on flat-or­bit in­jec­tion through the Lam­bert­son sep­tum and the cor­rect op­ti­cal match. Lon­gi­tu­di­nal­ly, en­er­gy spread in the boost­er is con­vert­ed to ar­rival-time dis­per­sion by the strong R56 com­po­nent in the trans­fer line. In this paper, we re­port on turn-by-turn imag­ing of the in­ject­ed beam in both the trans­verse plane and in the lon­gi­tu­di­nal di­rec­tion using a fast-gat­ed ccd and streak cam­era, re­spec­tive­ly.

• L. Wang, X. Huang, M.T.F. Pivi
  SLAC, Menlo Park, California

The Cor­nell Elec­tron Stor­age Ring (CESR) has been re­con­fig­ured as an ultra low emit­tance damp­ing ring for use as a test ac­cel­er­a­tor (Ces­r­TA) for In­ter­na­tion­al Lin­ear Col­lid­er (ILC) damp­ing ring R&D. One of the pri­ma­ry goals of the Ces­r­TA pro­gram are to in­ves­ti­gate the in­ter­ac­tion of the elec­tron cloud with low emit­tance positron beam, to ex­plore meth­ods to sup­press the elec­tron cloud, and to de­vel­op suit­able ad­vanced in­stru­men­ta­tion re­quired for these ex­per­i­men­tal stud­ies. This paper re­port the sim­u­la­tion of the elec­tron-cloud for­ma­tion in the wig­gler and quadrupole mag­nets using 3D code CLOUD­LAND. The trans­verse dis­tri­bu­tion of elec­tron cloud in a wig­gler mag­net is sim­i­lar to a dipole mag­net ex­cept in the zero ver­ti­cal field re­gions where the elec­trons have com­pli­cat­ed tra­jec­to­ries and there­fore a longer life­time. For­tu­nate­ly, these elec­trons are dom­i­nant­ly di­rect-pho­to-elec­trons and can be eas­i­ly re­duced by prop­er­ly ar­rang­ing pho­ton ab­sorbers. Sim­u­la­tions show that the elec­tron cloud in a quadrupole mag­net can be trapped for long time due to the mir­ror field ef­fect.

• A. Miller, D.R. Daranciang, A. Lindenberg
  Stanford University, Stanford, California
• W.J. Corbett, A.S. Fisher, J.J. Goodfellow, X. Huang, W.Y. Mok, J.A. Safranek, H. Wen
  SLAC, Menlo Park, California

By op­er­at­ing SPEAR3 in the quasi-isochronous (low-al­pha) mode, one can pro­duce syn­chrotron ra­di­a­tion with pulse du­ra­tions of order 1ps. Ap­pli­ca­tions in­clude pump-probe x-ray sci­ence and the pro­duc­tion of THz ra­di­a­tion. Mea­sure­ments of short pulse lengths are dif­fi­cult, how­ev­er, be­cause the light in­ten­si­ty is low and streak cam­era res­o­lu­tion is of order 2ps. Bunch ar­rival time and tim­ing jit­ter are also im­por­tant fac­tors. In order to fur­ther quan­ti­fy the pulse length and tim­ing sys­tem per­for­mance, a 5MHz, 50fs mode-locked laser was used to cross-cor­re­late with the vis­i­ble SR beam in a BBO crys­tal. The 800nm laser pulse was de­layed with a pre­ci­sion me­chan­i­cal stage and the prod­uct SHG ra­di­a­tion de­tect­ed with a pho­to­di­ode / lock-in am­pli­fi­er using the ring fre­quen­cy as ref­er­ence. In this paper we re­port on the ex­per­i­men­tal setup, pre­lim­i­nary pulse length mea­sure­ments and prospects for fur­ther im­prove­ment.

Slides

• Y. Cai, K.L.F. Bane, K.J. Bertsche, A. Chao, R.O. Hettel, X. Huang, Z. Huang, C.-K. Ng, Y. Nosochkov, A. Novokhatski, T. Rabedeau, J.A. Safranek, G.V. Stupakov, L. Wang, M.-H. Wang, L. Xiao
  SLAC, Menlo Park, California

Over the past year, we have worked out a base­line de­sign for PEP-X, as an ul­tra-low emit­tance stor­age ring that could re­side in the ex­ist­ing 2.2-km PEP-II tun­nel. The de­sign fea­tures a hy­brid lat­tice with dou­ble bend achro­mat cells in two arcs and the­o­ret­i­cal min­i­mum emit­tance cells in the re­main­ing four arcs. Damp­ing wig­glers re­duce the hor­i­zon­tal emit­tance to 86 pm-rad at zero cur­rent for a 4.5 GeV elec­tron beam. At a de­sign cur­rent of 1.5 A, the hor­i­zon­tal emit­tance in­creas­es, due to in­tra-beam scat­ter­ing, to 164 pm-rad when the ver­ti­cal emit­tance is main­tained at a diffrac­tion lim­it­ed 8 pm-rad. The base­line de­sign will pro­duce pho­ton beams achiev­ing a bright­ness of 10²² (ph/s/mm²/mrad²/0.1% BW) at 10 keV in a 3.5-m con­ven­tion­al pla­nar un­du­la­tor. Our study shows that an op­ti­mized lat­tice has ad­e­quate dy­nam­ic aper­ture, while ac­com­mo­dat­ing a con­ven­tion­al off-ax­is in­jec­tion sys­tem. In this paper, we will pre­sent the study of the lat­tice prop­er­ties, non­lin­ear dy­nam­ics, in­tra-beam scat­ter­ing and Tou­schek life­time, and col­lec­tive in­sta­bil­i­ties. Fi­nal­ly, we dis­cuss the pos­si­bil­i­ty of par­tial las­ing at soft X-ray wave­lengths using a long un­du­la­tor in a straight sec­tion.

• X. Huang, J.J. Sebek
  SLAC, Menlo Park, California

Turn-by-turn beam po­si­tion mon­i­tor (BPM) data from mul­ti­ple BPMs are fit­ted with a track­ing code to cal­i­brate mag­net strengths in sim­i­lar man­ner as the well known LOCO code. Sim­u­la­tion shows that this method can be a quick and ef­fi­cient way for op­tics cal­i­bra­tion. The method is ap­pli­ca­ble to both linacs and ring ac­cel­er­a­tors. We also show ex­per­i­men­tal mea­sure­ment of the trans­fer ma­trix with turn by turn BPM data.

• X. Huang, J.A. Safranek
  SLAC, Menlo Park, California

We use mea­sured or sim­u­lat­ed mag­net­ic fields for dipoles and quadrupoles to build a lat­tice model for SPEAR3. In a non-sym­plec­tic ap­proach the phase space co­or­di­nate map­ping on the fields is based on Runge-Kut­ta in­te­gra­tion of the equa­tion of mo­tion. In a sym­plec­tic ap­proach we ap­prox­i­mate the fields with prop­er fringe field mod­els. Com­pli­ca­tion of the use of rect­an­gu­lar gra­di­ent dipoles in SPEAR3 is con­sid­ered. Re­sults of the model is com­pared to mea­sure­ments on the real ma­chine.