• W. Fischer, E.N. Beebe, D. Bruno, D.M. Gassner, X. Gu, R.C. Gupta, J. Hock, A.K. Jain, R.F. Lambiase, Y. Luo, M. Mapes, W. Meng, C. Montag, B. Oerter, M. Okamura, A.I. Pikin, D. Raparia, Y. Tan, R. Than, J.E. Tuozzolo, W. Zhang
  BNL, Upton, Long Island, New York

In po­lar­ized pro­ton op­er­a­tion the lu­mi­nos­i­ty of RHIC is lim­it­ed by the head-on beam-beam ef­fect, and meth­ods that mit­i­gate the ef­fect will re­sult in high­er peak and av­er­age lu­mi­nosi­ties. Two elec­tron lens­es, one for each ring, are being con­struct­ed to par­tial­ly com­pen­sate the head-on beam-beam ef­fect in the two rings. An elec­tron lens con­sists of a low en­er­gy elec­tron beam that cre­ates the same am­pli­tude de­pen­dent trans­verse kick as the pro­ton beam. We dis­cuss de­sign con­sid­er­a­tion, pre­sent the main pa­ram­e­ters, and es­ti­mate the per­for­mance gains.

• P. Thieberger, R. Bonati, G.F. Corbin, J.P. Cozzolino, A.K. Jain, G.T. McIntyre, M.G. Minty, C. Montag, J.F. Muratore, C. Schultheiss, S. Seberg, J.E. Tuozzolo
  BNL, Upton, Long Island, New York

We re­port on re­cent de­vel­op­ments for mit­i­gat­ing vi­bra­tions of the quadrupole mag­nets near the in­ter­ac­tion re­gions of the Rel­a­tivis­tic Heavy Ion Col­lid­er (RHIC). High pre­ci­sion ac­celerom­e­ters, geo­phones, and a laser vi­brom­e­ter were in­stalled around one of the two in­ter­ac­tion points to char­ac­ter­ize the fre­quen­cies of the me­chan­i­cal mo­tion. In ad­di­tion ac­tu­a­tors were mount­ed di­rect­ly on the quadrupole cryostats. Using as input the lo­cal­ly mea­sured mo­tion, dy­nam­ic damp­ing of the me­chan­i­cal vi­bra­tions has been demon­strat­ed. In this re­port we pre­sent these mea­sure­ments and mea­sure­ments of the beam re­sponse. Fu­ture op­tions for com­pen­sat­ing the vi­bra­tions are dis­cussed.

• Y. Hao, P. He, A.K. Jain, V. Litvinenko, G.J. Mahler, W. Meng, J.E. Tuozzolo
  BNL, Upton, Long Island, New York

In this paper we pre­sent the de­sign and pro­to­type mea­sure­ment of small gap (5mm to 10 mm aper­ture) dipole and quadrupole for the fu­ture high en­er­gy ERL (En­er­gy Re­cov­ery Linac). The small gap mag­nets have the po­ten­tial of large­ly re­duc­ing the cost of the fu­ture elec­tron-ion col­lid­er pro­ject, eRHIC, which re­quires a 10GeV to 30 GeV ERL with up to 6 en­er­gy re­cov­ery pass­es (3.8 km each pass). We also stud­ied the sen­si­tiv­i­ty of the en­er­gy re­cov­ery pass and the align­ment error in this small mag­nets struc­ture and coun­ter­mea­sure meth­ods.

• B. Parker, M. Anerella, J. Escallier, P. He, A.K. Jain, A. Marone, P. Wanderer, K.-C. Wu
  BNL, Upton, Long Island, New York
• P. Bambade
  LAL, Orsay
• B. Bolzon, A. Jeremie
  IN2P3-LAPP, Annecy-le-Vieux
• P.A. Coe, D. Urner
  OXFORDphysics, Oxford, Oxon
• C. Hauviller, E. Marin, R. Tomás, F. Zimmermann
  CERN, Geneva
• N. Kimura, K. Kubo, T. Kume, S. Kuroda, T. Okugi, T. Tauchi, N. Terunuma, T. Tomaru, K. Tsuchiya, J. Urakawa, A. Yamamoto
  KEK, Ibaraki
• A. Seryi, C.M. Spencer, G.R. White
  SLAC, Menlo Park, California

The KEK ATF2 fa­cil­i­ty, with a well in­stru­ment­ed beam line and Final Focus (FF), is a prov­ing ground for lin­ear col­lid­er (LC) tech­nol­o­gy to demon­strate the ex­treme beam de­mag­ni­fi­ca­tion and spot sta­bil­i­ty need­ed for a LC FF*. ATF2 uses water cooled mag­nets but the base­line ILC calls for a su­per­con­duct­ing FF**. Thus we plan to re­place some ATF2 FF mag­nets with su­per­con­duct­ing ones made via di­rect wind con­struc­tion as planned for the ILC. With no cryo­genic sup­ply at ATF2, we look to cool mag­nets and cur­rent leads with a few cry­ocool­ers. ATF2 FF coil wind­ing is un­der­way at BNL and pro­duc­tion warm mag­net­ic mea­sure­ments in­di­cate good field qual­i­ty. Hav­ing FF mag­nets with larg­er aper­ture and bet­ter field qual­i­ty than pre­sent FF might allow re­duc­ing the beta func­tion at the FF for study of fo­cus­ing regimes rel­e­vant to CLIC. Our ATF2 mag­net cryo­stat will have laser view ports for cold mass move­ment mea­sure­ment and FF sup­port and sta­bi­liza­tion re­quire­ments under study. We plan to make sta­bil­i­ty mea­sure­ments at BNL and KEK to re­late ATF2 FF mag­net per­for­mance to that of a full length ILC R&D pro­to­type at BNL. We want to be able to pre­dict LC FF per­for­mance with con­fi­dence.

* ATF2 proposal, volumes 1 and 2 at http://lcdev.kek.jp/ILC-AsiaWG/WG4notes/atf2/proposal/index.html
** International Linear Collider Reference Design Report, ILC-REPORT-2007-001, August 2007.