Previous R&D of vibratig wire aligmet techique for HEPS WU Lei( 吴蕾 ) 1, WANG Xiao-log( 王小龙 ) 1,3 LI Chu-hua( 李春华 ) 1 QU Hua-mi( 屈化民 ) 1,3 1 Istitute of High Eergy Physics, Chiese Academy of Scieces, Beijig 100049, Chia Uiversity of Chiese Academy of Scieces, Beijig 100049, Chia 3 Doggua Istitute of Neutro Sciece (DINS), Doggua 53808, Chia Abstract: The aligmet tolerace of multipoles o a girder is better tha 30m i the storage rig of High Eergy Photo Source (HEPS) which will be the ext project at IHEP (Istitute of High Eergy Physics). This is difficult to meet the precisio oly usig the traditioal optical survey method. I order to achieve this goal, vibratig wire aligmet techique with high precisio ad sesitivity is cosidered to be used i this project. This paper presets some previous research works about theory, scheme desig ad achievemets. Key words: vibratig wire, aligmet, magetic field measuremet, accelerator, maget PACS: 9.0.db 1 Itroductio HEPS will be a 5 GeV, 196 meters circumferece third geeratio sychrotro radiatio facility with ultra emittace ad extremely high brightess. The emittace will be better tha 0.1mrad. The storage rig is a 48 cell 7BA lattice. Figure 1 is oe of 48 typical cells. The multipole girder that supports several quadrupoles ad sextuples is desiged 3.8 meters. But this is ot the fial value, the lattice is still i the desig [1]. Fig. 1. Oe of 48 typical cells. Table 1. HEPS aligmet tolerace. Toleraces Maget to Maget Girder to Girder Horizotal 0.03mm 0.05mm vertical 0.03mm 0.05mm Beam directio 0.5mm 0.5mm Roll agle 0.mrad 0.mrad Table 1 shows the aligmet tolerace i HEPS. It is difficult to achieve the required accuracy usig the traditioal optical survey. So vibratig wire aligmet techique is cosidered to meet the tolerace 0.03mm betwee maget to maget o oe multipole girder. Besides, automatic adjustmet girder ca help to achieve the tolerace 0.05mm betwee girder to girder. Vibratig wire techique has bee used i some differet projects i may labs. It has demostrated the potetial to measure the magetic ceter to the required accuracy. These applicatios of vibratig wire are based o the same fudametal priciple, but the specific purposes are distict. Vibratig wire is firstly be used at Corell Uiversity to fid the magetic ceter of supercoductig quadrupoles placed iside the cryostat for CESR []. Later, it has bee used to fid the soleoid magetic ceter [3] ad study the characterizatio of udulator magets [4]. I SLAC, this techique is used to fiducialize the quadrupoles betwee udulator segmets for LCLS [5] ad alig quadrupole for FFTB. I CERN, its applicatio is soleoid magetic ceter fidig [6]. I PSI, vibratig wire is used to fid the magetic axis of quadrupoles for Swiss Free Electro Laser [7]. I BNL, this techique is used to alig the quadrupoles ad sextupoles o oe girder for NSLS-II [8]. Vibratig wire is based o measuremet of the magetic axis to alig the magets. It is a further evolutio of pulsed wire method. The simple diagrammatic sketch is like Figure [9]. The specific priciple of this method is like that: a sigle coductig wire is stretched through the maget aperture ad drive by a alteratig curret. Trasversal vibratios are cotiuously excited by period Loretz Force. By matchig curret frequecy to oe of the resoat modes of wire, the vibratio amplitude ad sesitivity are ehaced ad the magetic iductio itesity at the wire positio ca be calculated. Move the wire across the aperture i horizotal directio(x) or vertical(y) directio,
the magetic iductio itesity distributio ca be gotte ad the magetic axis ca be foud. y (,) z t Y ()exp( z it) d IB z Re si( )exp( it). ( i) l 1 B 0 x. Vibratig wire test bech model (4) Fig.. Diagrammatic sketch of vibratig wire. Research developmet So far, the mai research developmet is related to the research work about theory ad scheme desig, icludig derivatio of basic theory, desig of test bech model, desig of sag measuremet scheme, calculatio of vibratig amplitudes, desig of sesor circuit ad sesor calibratio ad desig of data acquisitio ad cotrol system..1 Basic theory Fig. 3. Force aalysis of a sectio of wire dz. Accordig to Newto s law, the differetial equatio of the motio of a sectio of wire dz i y-z plae (Figure 3) is: y y y T g B ( ) x z I0 exp( i t). t z t is the mass per uit legth. T is the wire tesio. is the dampig coefficiet. Solvig the differetial equatio, the homogeous solutio is: y z t z Ae t t h (,) Resi( )[ cos ( ) 1 l t + Be si ( ) t)]. The particular solutio due to gravity is: 1 (1) () g g yg ( z) z( zl) z( z l). (3) T 8 f l The particular solutio due to Loretz Force is: Fig. 4. Vibratig wire test bech model. Figure 4 is the desig of vibratig wire test bech model. The whole test bech is composed of two parts which are ed bech ad maget support girder. The differece betwee fixed ed bech ad free ed bech is the fixed way of the wire. At the fixed ed, the wire is fixed ad located by V otch. At the free ed, the wire is pulled by weights through a pulley ad also located by V otch. O each ed bech, there are two traslatio stages ad two sesors. The horizotal stage moves wire i x directio ad the vertical oe for wire movemet i y directio. The horizotal sesor detects the wire vibratio amplitudes i x directio ad the vertical oe for y directio. Vibratig wire is 0.15mm diameter wire made with alloy of copper-beryllium. The maget support girder is desiged 5.4 meters. Two parallel guideways are istalled above the girder i order to move magets coveietly. By move magets alog the guideways, the magetic ceter could be detected i differet place alog the girder. The quadrupole ad sextupole are borrowed from BEPCII for lack of magets made for HEPS. They are 105Q ad 130S..3 Sag measuremet scheme For a 7 meters log wire, sag is uavoidable because of self-weight. It is about several hudred micros. To fid the vertical magetic ceter, accurate sag correctio is essetial. Figure 5 is the sag measuremet scheme. The method is to establish a coordiate system relative to the wire ad the measure the sag at differet place alog the wire (z directio). Use laser tracker ad NIVEL00 to adjust the positio ad orietatio of the sesor. Make the sesor the same attitudes i differet place. Use sesor to measure the vertical positio of the
wire. addig filters to the circuit ad DAQ program is uder cosideratio. Fig. 5. Sag measuremet scheme..4 Sesor circuit ad calibratio The product model of the sesor i HEPS is GP1S094HCZ0F. It is a photoiterrupter with opposig emitter ad detector i a moldig that provides o-cotact sesig. The fuctio of the sesor is to detect the vibratig amplitudes y d (z,t) chage over time due to Loretz Force. Because the sesor is just a simple electro compoet, the sesor circuit is desiged to make the output voltage appropriate. Fig. 7.: Shadig Voltage of Sesor. Table. Shadig voltages of sesor. Left liear Right liear Voltages(V) 9.45 5.8 5.58 9.7 Voltage differece(v) (mm) 3.65 3.69 0.18 0.3 0.38 0.5 differece(mm) Voltage/displace -met(mv/m) 0.1 0.1 30.4 30.75. Fig.6. Sesor output test bech. We do the sesor calibratio o sesor output test bech (Figure 6). By chagig the positio of the sesor relative to the wire o the sesor output test bech, a series of poits which are the output voltages were gotte. Because the sesor received differet optical sigals whe the wire at differet locatios, so the output voltages are differet. Figure 7 ad 8 is the outputs of oe of four sesors that were tested. The results were summarized i Table ad 3. There are two liear output parts. I each part, the wire displacemet is about 0.1~0.1mm. Oe part will be chose as the workspace. There was little differece i the output voltages betwee coverig the sesor with light shield ad exposig the sesor i the lab light. But the voltages were more stable whe the sesor was covered. The sesitivity of the sesor is approximately 30mV/m. I oe test positio, the measures of variatio reduced from 0mV to 6mV after filterig. The stability has improved sigificatly. So Fig. 8. No shadig voltages of sesor. Table 3. No shadig voltages of sesor. Left liear Right liear Voltages(V) 9.1 6 5.56 9.7 Voltage differece(v) (mm) differece(mm) Voltage/displace -met(mv/m) 3.1 3.71 0. 0.3 0.38 0.5 0.1 0.1 31 30.9
.5 Calculatio of vibratig amplitudes Vibratio amplitudes should be cotrolled withi the voltage liear output part. Ad it also should be make full use of this. Accordig to the measuremet, the liear width is about 0.1~0.1mm. We desiged the wire vibratio amplitudes 0.045mm. Accordig to equatio 4, the equatio of measuremet of quadrupole magetic ceter is deduced: I Gl z ymax ( z) [ si( )si( )] y. l j l 0 Q (5) Ad we do measuremet of sextupole magetic ceter usig the equatio 6. IBl '' z ymax ( z) [ si( )si( )] x. l j l 0 Q (6) I 0 is the wire curret amplitude. Gl Q is the quadrupole itegrated gradiet. l Q is the quadrupole legth. is the resoace order. is the harmoic frequecy. is the dampig costat. J equals l / z maget. l is the legth of the wire ad z maget is the locatio of the maget alog the wire. B l Q is the sextupole itegrated gradiet. y is the distace betwee magetic ceter relative to the wire i y directio ad x is the distace betwee magetic ceter relative to the wire i x directio. I short, accordig to the distace betwee the magetic ceter ad wire, the distace betwee wire ed ad maget, the distace betwee wire ed ad sesor, ad magetic field gradiet, the AC curret ca be calculated. We use this method to estimate the AC curret i the wire accordig to the previous magetic survey datum of the magets borrowed from BEPCII..6 Data acquisitio ad cotrol system The figure 9 is the scheme of the data acquisitio ad cotrol system. There are four iput sigal rages i DAQ card PXI-61. The samplig rate is 500Ks/s per chael. Its fuctio is to sample sesors ad 1 drivig curret sigals simultaeously. Datum will be trasported to the IPC by the commuicatio cards PXIe- 8360 ad PCIe-836. IPC also cotrols the movemet of x-y stages. We use LabVIEW software to do data acquisitio ad data process. Fig 9. Scheme of data acquisitio ad cotrol system. 3 coclusios The aligmet tolerace of multipoles o a log girder i HEPS should be better tha 30 micros. Vibratig wire aligmet techique is appropriate to achieve the required accuracy. This techique has ever bee used i Chia. May research works have bee doe to study the techique. I this article, we itroduced the backgroud of the magets aligmet i HEPS ad previous research work ad achievemets. Refereces [1] Feasibility Report of HEPS.014 [] Temykh Alexader, Vibratig wire field measurig techique, Nuclear Istrumet ad Methods i Physics Research A, 1997. 399: 185-194 [3] Bottura L., Buzio M, Pauletta S et al. Measuremet of Magetic Axis i Accelerator Magets: critical compariso of methods ad istrumets. IMTC 006 [4] Temykh A., Levashov Y, Wolf Z. A Study of Udulator Magets Characterizatio Usig the Vibratig Wire Techique, Nuclear Istrumets ad Methods i Physics Research A, 010. 6: 650-656 [5] Wolf Zachary. A Vibratig Wire System for Quadrupole Fiducializatio, SLAC-TN-10-087. 005 [6] P. Arpaia, Beaumot A, Defere G et al. sigle-stretched ad vibratig wire measuremets at CERN, IMMW18, 013 [7] Wouters C., Calvi M, Vrakovic V et al. Vibratig Wire Techique ad Phase Lock Loop for Fidig the Magetic Axis of Quadrupoles, IEEE Trasactio o Applied Supercoductivity. 01
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