A High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Applications

Transcription

1 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 A High Precision Double Tubed Hydrostatic Leveling System for Accelerator Alignment Alications S. Singatulin, J. olk,. Shiltsev Fermilab, Batavia, IL 651, USA A. Chuyra, A. Medvedko, M. Kondaurov Budker Institute, Novosibirsk 639, Russia Since 1998 several hydrostatic leveling system (HLS) systems have been installed in different locations on the Fermilab site. This work was in collaboration with Budker Institute and SLAC. All systems were either halffilled (HF) or full-filled system. Issues assembling HLS are covered in this article. Imroved and cost-effective water system with temerature stabilized of water media, named double-tubed DT-FF, resented as an alternative to HF, and as net derivation of FF HLS, esecially for interaction region of accelerators. 1. DOUBLE TUBED FULL FILLED (DTFF) HLS With the increased requirements of accelerators alignment accuracy of hydrostatic leveling systems are used as a oint of the sace reference [1]. More and more of these systems are based on half filled water ies []. Users rarely use or roject systems based on full filled ies. The main reason is uncertainties of measurements from the liquid circuit, due to the combination of both thermal gradients along circuit and liquid dilatation. Since water secific mass changes with temerature (ecet for water close to 4 C) and because temerature is not measured everywhere along the water circuit between communicating vessels, the measurement uncertainty Δz is sourced by all vertical arts of water ies, as a consequence of the different temerature between these arts. The following icture shows variation of water density relatively to density on 4 C. Figure 1. Water density 1

2 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 For eamle, at T C a temerature difference of ΔT 1 C between two vertical branches of water circle (vertical comonent amlitude h 1 cm) induces Δz μm (a vertical dearture of water surface osition in the two vessels. At Fermilab eerience with half filled systems has given much information about the disadvantages and advantages of two different systems. In following Table 1 the author has tried to classify them. Table 1 Proerties Full Filled Half Filled Double Tubed Full Filled(suggested) Temerature stability Deend from Ecellent Ecellent temerature Material of tube Cheaer, transarent Plastic High cost Stainless tubes Cheaer, transarent Plastic Common shield for water tubes Length length L Length L 3L Suorts No Strong suort No Tube Mounting Simle In some location It is Simle imossible! Labor-consuming, Suorts Realignment Additions Nothing Cleaning of tubes, Alignment tools Need water recirculation system in Total: Good accuracy Low Cost Ecellent accuracy High cost one of tubes Ecellent accuracy Accetable in cost Double tube system uses two tubes with water and one tube with an air circuit. The first tube is for levelling measurements, the second tube aralleling the first tube has water circulating in it by means of a um and is used to maintain a constant water temerature. In this way we eclude temerature gradients in water circuit. In addition the water could ass through the base of the ools to stabilize the sensors and electronics. As consequence of those two stes it is ossible to realize high recision double tubed hydrostatic levelling system. Circulating water in second tube instead in original water tube ecludes dynamic disturbing of water level and thereby receiving data from sensors instantly.

3 9th International Worksho on Accelerator Alignment, Setember 6-9, 6. MI8 HLS HALF-FILLED SYSTEM There were many HLS system installed at Fermilab. One of them was mounted in tunnel MI8 [3] in 1. The system consisting of sensors SAS [4], located along a tunnel of Main Injector in section MI8 [3] for a total length of 3 meters. In this system transarent lastic ies were used, with an internal diameter is 5.4 mm (one inch). The system also had a test device, allowing adding or removal of water. This device allowed managing the water level remotely by using RS485 serial card from PC under a rogrammed algorithm. The Test Device allows testing dynamic behavior and is very effective in testing system. Mechanics of TD for the system tests is reresented in figure. Submersible Cylinder (7) is mounted on rod (6) and laced in tank (9) filled with water, which has one connection to tube line of the HLMS. ertical osition of the Cylinder is defined by rod bearing (5). Rod is moved by micrometer (4), which shifts on 1 mm er every turn of motor rotor (1). Connection between the rotor and micrometer is made through couling (3). All above-mentioned arts are fied on latform (). ertical osition of mechanism is established with hel of the latform tilting screws (8). All arts inside water tank are made from stainless steel materials. Water tank has additional hole on to for balancing air ressure inside and outside of tank Figure. Test Device at SLAC 3

4 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Figure 3 shows the dynamic reaction of levels, when mean level of water derived by removing from the one end of system close to sensor L. HLS system had stabilized in ga +/- 1 micrometers just after 15 hours with shifting of mean level 1 micrometers. Figure 3. Ste reaction HLS in MI8 3. MODELLING OF HLS Many modern system need to be stabilized in real time in sace and control ositions by movers. Is it ossible to redict the behavior of these systems? For vertical control very often used HLS system as sensor in feedback. We suggest simulating HLS to define in what frequency band HLS is alicable. Another advantage of modeling is to redicted behavior of system before construction of the system to eclude unforeseen circumstances and to avoid significant material charges. Modeling also hels to understand rocesses that occur in eisting systems. Let s consider laminar flowing of a Newtonian incomressible viscous liquid (water) in a ie in length l in diameter u ends (model of a simle level gauge). Forces resent: D < l in a gravity g with looking Inertia: Shear: π π D ; 4 D l ρ d l η ; dr 4

5 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Gravity: gy πd ρ ; 4 where ρ water density, η absolute coefficient viscosity, mean velocity, y mean level difference. Momentum balance is: d y ν d dy g y dt D dr dt L ν η - cinematic viscosity. ρ where (1), Since y means average in cross section, make substituting: d dy dr dt D where R R d d 1 d y dy ydr dr dt R (), dt R D dt is ie radius. Using () give us equation: d y ν dy g y dt D dt L In other form:. d dt dy y + ω dt ω g l 4 v ω D, + ω y, Decision of equation: 1 t ( ω + ( ω ω )) t ( ω ( ω ω )) y ( t ) C e + C e + C To simlify, take y() and ( t ) y( t) C e ωt We have to case: sinh 1) ω ( t ( ω ω )) y, so we have C C C tω ω > > y( t) Ce sinh t ( ω ω tω iπ / ω y( t) Ce sin t ω ω ) ω ; 3 1 and C 3. (sinh sine hyerbolic) 5

6 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Since we have at the end of ie vessels with other diameter D, we have to make additional substitution g l ω to ω. g l D D Estimations with a ie 3 9.5[mm] and D 77[mm]. If l m(1 foot s) gives value ω. 7 and. 44 ω when D ω > ω flow has over-damed resonse of water circuit and has no self resonance vibrations. So finally levels behavior look could be fitted with eonential equation: y( t) ω1 t ω t Y1e + Ye. (*) To make an analogy in the resulting equations of an electric current I (U) circuits with connected inductance, resistance and caacitors it is ossible to receive electric model (fig. below) with the lumed arameters. L R C Here: ρl S πνρl L, C, R, S P - cross section area of ie, S - cross section area of ρg S S P vessel. The ressure difference ΔP is analogous to the U voltage, volume flow rate Φ is analogous to the current I. For system from n gauges with levels H I the electric model of the scheme reresented in figure is used: S U and average of seed of water in a ie ρg L1 R I1 A L R I A U1 C1 U C Un Cn On following ictures resented measurements and fitting result of fully filled HLS system with length 3 and 6 meters. The system contains two SAS level sensors connected by olyethylene ie with 1.7 mm O.D. (1/ inch O.D.) and length of 3 or 6 meters (1 or feet). Fitting gives decrement values τ 3 and 98 seconds on ies length 3m, 6 and 188 sec. - on length 6 meters. Proortional deendence τ from length is not followed from the resented above relation for ω.that is question for further study. Nevertheless we can use analogues with electric model. 6

7 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Figure 4. Over daming behavior of HLS with length 6M Figure 5. Over daming behavior of HLS with length 3M 7

8 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Figure 6. Dynamic eamle of half filled system On Fig.6 resented the same fittings rocedure for half filled tubes. This system has long setu time. Also fitting equation gives two essentially different decay times: first is about 5 minutes, second 3 hours. Half filled HLS system are slowly in resonse and single ie system have be to suorted very well to eclude sag when water is ut in the system. Thus, it is ossible to model comle HLS systems dynamic behavior as an electric system, drawing corresonding analogies and numerical transformations. The roblem is facilitated also by the fact that many CAD systems have the caability to simulate behavior of assive and active elements. To draw similar analogies of system with half filled ies is difficult enough since of resence two-hase media in ies. Nevertheless it also is obviously ossible. Thus, having measured once arametrical values used ies on unit of lengths and gauges itself on the test facilities stand, it is ossible to model behavior HLS and more accurately to interret measurements. 4. CONCLUSIONS We suggest Double tubed full filled system for vertical alignments, as cost effective solution for high recision hydrostatic levelling system instead of half filled. Accuracy results by the hel stabilizing temerature in all system. The arametrical model, accetable for full filled and double filled HLS is offered. Half filled HLS has higher time setu relatively to full filled. 8

9 9th International Worksho on Accelerator Alignment, Setember 6-9, 6 Reference [1] D.Martin, D.Rou, Real time altimetric control by a hydrostatic leveling system, Proc. of II IWAA, DESY, Hamburg, 199. [] W.Coosemans, F.Francia, essels, ies, water for recise alignments inside LEP, Graviton (Geneva, Switzerland), Setember 1994,.14. [3] A.Seryi, et al., Long term stability study at FNAL and SLAC using BINP develoed hydrostatic level system, Proceedings of the 3 Particle Accelerator Conference. [4] A. Chuyra, M. Kondaurov, A. Medvedko, S. Singatulin, E. Shubin, SAS family of hydrostatic level and tilt sensors for slow ground motion studies and recise alignment, IWAA4, CERN, Geneva, 4-7 October 4. 9