Coosemans, Williame

Juravlev, V M

Ramseier, G

Seryi, Andrei

Sleptsov, A I

Wilson, Ian H

CERN Document Server

SL/Div Reps6 july 1994 OCR OutputGeneva, SwitzerlandBranch INP Protvino, Russia27.6-1.7.94Fourth European Particle Accelerator Conference (EPAC 94), London, United Kingdom,significantly increase the level of vibrations.been shown that essential systems such as water cooling and ventilation plants canbut requires the tunnel to be built on a site which has a continuous and solid rock structure. It hascorrelation over long distances will certainly simplify the linear collider alignment problemmicron but the correlation at this frequency is very good up to a distance of 3km. Goodfrequencies the amplitudes are greater, at about 0.1 Hz the amplitude of vibration is almost 1at high frequencies (10-100 Hz) for distances of more than a few tens of meters. At lowfrequencies >10 Hz not exceeding 0.1nm. The results show that spatial correlation disappearsshown to be one of the quietest accelerator sites in the world with rms amplitudes forResults of seismic vibration measurements made in the LEP tunnel are presented. The LEP site isAbstractW. Coosemans, G. Ramseier, I. WilsonV.M. luravlev, A.A. Sery, A.I. Sleptsov*Seismic Vibration Studies for Future Linear CollidersCERN-sr-94-41 3W 5) if ’ iflllllllllllllllllllllllllllllllllllllIllllllllllllllllllCLIC Note 234CERN L1BRARiEs, GENEVA CERN SL/94-41 (RF)CERN - SL DIVISIONEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHfor both the LEP and UNK tunnels. OCR OutputThe data acquisition system consists of CAMAC modulesvibrations with frequencies >lO Hz does not exceed 0.1 nmThese probes measure vibrations in the 0.1-100 Hz band.spectrum shown in Fig.2 we see that the rms amplitude ofspeed with which they oscillate in a known magnetic field.prevailing weather above the ocean. From the integratedThe voltages induced in these coils are proportional to thepeak depends on the distance from the ocean and on the[1]. The probes are essentially pendula carrying small coils.waves of nearby oceans on the land. The amplitude of thesingle-axis seismic probes which are described in detail in(the "micro-seismic peak") is attributed to the action of theAll results were obtained with the Russian-made SM-3KVhigher than LEP and UNK.'I`he peak in the 0.07- 0.2 Hz bandthe T'1`2A tunnel which is on the main CERN site is much2. EQUIPMENT AND METHODusually manifests itself, i.e. at f > 1Hz, the vibration level inIn the frequency band where the so called "cultural" noisevibrations over long distances.measurements in the UNK tunnel were made at about 25m).this work has been placed on the spatial correlation ofis quieter - this is because LEP is deeper underground (theNorth-West of the centre of Geneva. The main emphasis inapproximately the same, in the 2-10 Hz band the LEP tunnelkm to the North of the CERN main site and 11 km to thespectra of vertical vibrations in the LEP and UNK tunnels arecompact, homogeneous, hard and dry. It is situated about 7The figure shows that whereas in the 0.3-100 Hz band thefrom test borings made many years ago is known to bepan of the tunnel was bored out of the "molasse" rock andFig.1 Power spectrum of vertical seismic vibrationsthis is where the tunnel goes under the Jura mountains. Thistunnel (about 120 m and 80 m underground respectively)collider. Points 4 and 5 are the deepest points of the LEPFreooencydzconditions that will exist in the tunnel of a future linearT 0 1 00tunnel during a shutdown and are more representative of the Stowere made in the arc between points 4 and 5 of the LEP $10l · Hrs.gives the results of a second series of measurements which $10l0transfer tunnel) and have been reported earlier [1]. This paper10measurements were made in the 'I’I`2A tunnel (an old beam XR A Atlt . ,,__wt‘10levels on the CERN site began in 1992. The first series of ..,_.t t~t» .lO `““**l‘¤*#tCERN and INP (Protvino) to measure seismic vibration1Ocharacteristics of seismic vibrations. A collaboration between 1Ofew nanometres requires a thorough understanding of the 1O-- rr2Aand to make head-on collisions with vertical beam sizes of a lOLEP-2%lOinteraction point of any future high energy e`*’e‘ linear colliderUNKg l1`°·.To be able to transport low emittance beams to thelOto?1. INTRODUCTIONFig.l with results obtained in the TT2A and UNK tunnels.plants can significantly increase the level of vibrations.tumed off. The results for vertical vibrations are compared inessential systems such as water cooling and ventilationnight at the weekend with all accelerator systems and devicescontinuous and solid rock structure. It has been shown thatLEP tunnel for quiet conditions. "Quiet " means during therequires the tunnel to be built on a site which has aPower spectra of seismic vibrations were measured in thecertainly simplify the linear collider alignment problem butdistance of 3km. Good correlation over long distances will3. RESULTS OF MEASUREMENTSbut the correlation at this frequency is very good up to aabout 0.1 Hz the amplitude of vibration is almost 1 micronrelationships are given again in the Appendix.of meters. At low frequencies the amplitudes are greater, atdescribed in [1]. For completeness the main expressions andfrequencies (10-100 Hz) for distances of more than a few tenstaking (few ms accuracy). Data treatment methods areresults show that spatial correlation disappears at highwas used to synchronise the start, stop and timing of dataamplitudes for Bequencies >10 I-Iz not exceeding 0.1nm. Thetimer connected to both systems via two 1.5km long cablesof the quietest accelerator sites in the world with rmsacquisition systems placed up to 3km apart were used . ALEP tunnel are presented. The LEP site is shown to be onethe spatial correlation measurements two identical dataResults of seismic vibration measurements made in thecomputer and special INP software (for details see [1]). Forspecially built for this application by INP, an IBM PC ATAbstractCERN, Geneva, SwitzerlandW.C00semans, G.Ramseier, I.Wils0nBranch INP Protvino, RussiaJuravlev V.M, Sexy A.A, Sleptsov A.I.Seismic Vibration Studies for Future Linear Collidersstructure. root mean square amplitude of vibrations with frequencies OCR OutputLEP tunnel there are no serious breaks in the Earth's surface seismic vibrations in "quiet" conditions to be very low - thecorrelated. This indicates that at least in this region of the Measurements made in the LEP tunnel show the level ofdistance of 3000m the micro-seismic signal is still wellspectrum as the distance between probes increases. Even at a 4. CONCLUSIONSdecrease in correlation of the high frequency part of theThe correlation spectra in these figures show a smooth reduce vibrations to acceptable levels.would have to be designed and situated more carefully toFig.3 Correlation spectra for vertical vibrations a factor of one hundred. For a linear collider such systemsvibration level - at some frequencies the level is increased byThe ventilation system has a strong influence on theO 1 1 iq 0 1 1 10A F1€q(1··1;) Distance 200Om Q1 O1 F1eq(Hz) Distance 3000m I `Fig.5 Ratio of vibrations for ventilation system on and offF, 1-1220 70 120 voz E 1 , z { Q M 2 : M1 i " I *9; vi 1 E 01 1, 1 52 os *11 s 1 a 1 11* o 1 ' Q l 11 O /»-=\r` 1 O i ;,_1/1.11i. ·i1:·i`<Y1&O.1 1 1 O l OO O 1 l 1 O 9 ""1 O 0_ Freq (Hz) Distance 200mFVSQ (HZ) Distance Om l· Q [ . *at 1 F'h1 1% w(J: M’ " ZJL} .4: 5 3 U Qi i iE ¤ =5 0 ul800m from compressor stationzi} `li *¥*”»’ha200m from compressor station1 O ¤1.O1_ ——- , weextemal electromagnetic noise during the day.correct (especially if the probes are not moved or touched).time correlation, this is because there is an increased level offrom the same probe is used the data obtained is probablyfrequencies the night-time correlation is better than the dayregion of the probes but since only the ratio of two spectraaccurate correlation measurements difficult. At somecovers a frequency band which is outside the normal workingcomparable with the very low level seismic signal and makespoint 4 ) is shown in Fig.5. The data in these two figuresbeing so quiet, the noise of the electronics becomesThe influence of the ventilation system (measured nearlarge enough. At high frequencies however (70-100 Hz), LEPconfirm that in the 0.07-70 I-Iz band the signal-noise ratio isFig.4 Ratio of vibrations for water cooling station on and offThe correlation spectra of the probes placed togethernight time and day time measurements respectively.F. F1 2shown in Fig.3. The solid and dashed lines correspond to0 50 100 150 200spectra for distances between probes of 0 to 3000 m aresimplify the linear collider alignment problem. Correlationy Q ——-- transverse viryrotnonsGood correlation over long distances will certainly 1 ; vertical viorotions bl 1 ’1_‘ 1* 11 1Fig.2 Integrated spectrum of vertical vibrations , ~ .11·1}1· 1,_ ,_ \` E M _ ixyehl1 i 1 ‘ 1* , · ya V N % N `i ‘ Il lii + 1,1FrequencyhzW3 1 1 10 100 H *1, gt 11 1 1 X11,. in $:.1<l'» 111 i 1 . 1· 1 1 ,51 { _» 1 ( 3/1 Q1 x [nil i` F1 ' J ` `1` ` iii‘— 11:.¢{f· 11S I ‘. rx -52<_> I ill]CdW1 "j \`\ \ \ ` -.vertical vibradons increased by a factor of three or four.10 is \800 m from the other. At some frequencies the level of- - Tm annex of the tunnel about 200 m from one of the probes andA __ ¤é‘Lapthe effect of tuming on a water cooling station situated in anUNKof the accelerator will create additional noise. Fig.4 shows1 9. 3auxiliary systems which are required to run during operationAlthough the LEP tunnel is basically a very quiet placeamplitudes.frequencies make the major contributions to the overall "coherence" OCR OutputInspection of the power spectrum readily indicates which N12(f) we called "correlation", and the modulus of NlZ(f)on different measurements respectively. The real part ofwhere ' and <> means complex conjugation and averagingT r0 =— j|x(t)\ dt= |P(f) df for (x)=02 I ‘ 2 `t>i;<f>= I-im<1i(f> q<f><l§> T->¤¤ Tintegrating over the frequency rangesignal) can be obtained from the power spectrum by where pu (f) is the mutual power spectrumvariance oz (the most important characteristic of a random(PSDV) and has units of (ttm/s)‘/I-Iz. The dispersion or ;/(PiXPz>as defined above is the velocity power spectral density Nlz(f) = <pl2>The measured variable x(t) in this work is velocity and P(f)by a factor 2. domain is given as followsdefinition of power spectrum density and therefore multiply The nomtalised cross-correlation function in the frequencyfunction we limit ourselves to positive frequencies in ourSince the power spectrum of a real signal is a symmetrica(1.’) = |P(f) e df+°° . ·lmqu`) = Ixn) e·*¤" dtP(f) = |a(·r) e dr+¤¤ _ .`mnwlwre transformations:is connected to the power spectrum via the FourierT -9 <>¤T->¤·¤T T. a(·t’) = 2Lim— fx (t) x(t+ T) dtP(f) = 2 Lim- Iq(f) 1 2 ..process :Power spectral density is defined as follows:The autocorrelation function (non-normalised) of a random6. APPENDIXPff) = 2q<f> I<ll |2> TCERN SL/93-30, CLlC—Note 191.CERN ”l'1`2A Tunnel for the Linear Collider Studies"many measurements are averaged.Chroco. "Measurements of Seismic Vibrations in thein order to find the power spectrum with some precisionW.C00semans, G.Ramseier, l.Wilson, V.Lawsonln practise however the time of measurement T is limited. So[1] V.Ba1aldn, V.Juravlev, A.Sery, A.Sleptsov, Y.Valiaev,integrated spectrum has the dimension [micron].5. REFERENCESIf the power spectrum is defined in [micron-;/Hz] then thefcontinuous and solid rock structure. I(f) =\J jpsodtmrachieved if the tunnel is built on a site which has afmaxthe linear collider alignment problem but can only beGood correlation over long distances will certainly simplifyat this frequency is very good up to 3km. spectrum from —ss or fmax to the frequency of interest.amplitude of vibration is almost l micron but the correlation rms displacement can be determined by integrating theamplitudes are greater, at about 0.1 Hz for example the and the contributions of the various frequencies to the totalfrequencies is however small. At low frequencies thethan a few tens of meters. The vibration level at thesefrequencies (10-100 Hz) for distances between probes of more gm = X] _|·PSDd (f)dfThis study has shown that the correlation disappears at highcollider. displacement Znng is given byof such systems is clearly necessary for any future linearform of a PSDd is particularly useful since the total rmsincrease the level of vibrations. A careful design and locationthe local circular frequency. A presentation of results in thecooling plant and ventilation systems can significantlyhas units of ttmz/Hz and is defined as PSDV / mz where to isbeen shown however that essential systems such as waterThe associated "displaeement" power spectral density PSDdgreater than 10 Hz for example does not exceed 0.1nm. It has

Seismic vibration studies for future linear colliders

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