Abstrflct -High-gradient snpcrconducting quadiupole magnets me hcjng devcloped by thc US LIIC Accclcrsior Projca for thc Interaclion Rcgions of the Largc Hadron Collider. Dctcrininntion of the magnetic iixis lor alignmcnt of thcsc magnets will hc performed using n singlc stretcticd wire systcm. These incnsuremcnts will be dnne both a1 mom and cryogenic temperatures with very IOJI~ wire lenglhs, up to 20111. This paper repork on thc stretchcd wire alignmeiit tncthodology to be employed and thc resiilts of rccerit rontn-fciiipcraliire mc:isuretnents on n 2 m modcl magnci wiili long wirc lengths.
INTROUUCTKIN'l'lic low-p insertion qnadrupoks currently under tlevelopmcnt at PNAL and KBK will have their alignment parameters metisurcd after being installed in cryostats at PNAL. As these magnets providc the final focus before collision for thc LHC beam, thclr alignment tnust be accurately determined. Such dignincnt measurements are required at both room and cryogenic temperatures because only thc FNAL magnets will undergo testing at cryogenic temperatures; thc remaining tnagncts will rcly on warm alignnicnt measu.cmcnts and measnreincnt of the correlation betwecn warm and cold alignment parameters. Purthermorc, although the length of thc MQX magnet assemblies rangc from 5.5 to 6.5 m, the Q2 has two such lnilgnets and a corrector package housed wiihin R singlc cryostat approximatcly 15 m in length. When mountcd on B tcst stand, with cryogcnic etid cans, aligiiment measurements inust be performed within ii beam tube o f length -20 m.The alignment device chosen for these tneasurcments is i\ SiIiglc Stretched Wire (SSW) systcm of the type used nt IlIiSY for thc HERA qiiadrripules [ I ] and for the Main Injector quadrupoles at PNAL [ 2 ] . Thc goals for rhe systcm arc tneasurcinent in the transvcrse planc of the average quadrupole axis (vertical and horizontal) to 50 ptn and roll to 100 p a d (including transfcr to magnct l'irlucials) under thc mcnsurement conditions cited abovc, hi additinn, in order to place the Q2AiQ2B device SO as to minimize thc eFFects of relative misalignments of the scparnte elcments (which cannot be adjusted after installation i o the cryostat), the true axcs of the individual Q2AlQZB magnets innst also be determined (ratlicr than just their average centers). This papcr outlines the syslem and techniqucs that will be used to achieve these measurement rcquiretnents and prcacnts the rcsults of recent tcsts o f thc methods involved.Manascripl rcccivcd Scptcinbcr 27. 1999. Work supportcd hy tlic U S . Dclurtnicnr uf Ewrgy.A single wirc is stretchcd between two sets r)f precision motion stages ils shown sclicmarically in Fig. 1. Thc return wire of the loop lics fixed on the bottom of the beam pipe or outside the magncr. Fig. I . Cnordinntc definitions fur SSW and inognel systcniThe vcctor potential at the ccnter of thc quadrupolc field of gradient ,p can bc expressed as where 11, b,,, a, arc thc multipole order, and normnl and skew coefficients, R is the rcference radius, x.y arc the huriiontal and verti...
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