Fine Beam Tube. Introduction. Functional principle

Transcription

1 Fin a Tub Intoduction fin ba tub consists of a sphical glass plung filld with nobl gas und low pssu. n lcton gun insid th tub (cathod, contol gid and anod) gnats a ba of lctons. Th ba stiulats gas olculs to th ission of light, whby th ba bcos visibl within th tub. Th agntic fild of two Hlholtz coils focs th lctons onto a cicula path that allows us to dtin th spcific chag /. Functional pincipl Th souc of th lcton ba is th lcton gun, which poducs a sta of lctons though thionic ission at th hatd cathod and focuss it into a thin ba by th contol gid (o Whnlt cylind ). stong lctic fild btwn cathod and anod acclats th lctons, bfo thy lav th lcton gun though a sall hol in th anod. Th fin ba tub contains hydogn olculs at low pssu, which though collisions with lctons a causd to it light. This aks th obit of th lctons indictly visibl To donstat dflction in agntic filds and calculat th spcific chag / th fin ba tub is placd in a agntic fild of two Hlholtz coils. Magntic fild (dipol) Elcton gun nod CERN Tachs Lab

2 Fin a Tub Stup Equipnt 1 Fin ba tub 1 Hlholtz coils with hold and asuing dvic 1 DC pow supply V 1 DC pow supply 0 0 V 1 Voltt, DC, < 300 V 1 t, DC, < 3 1 Stl tap asu, 3 Safty conncting lads, 5 c 3 Safty conncting lads, 50 c 7 Safty conncting lads, 100 c additionally condd: 1 Tslat, 1 xial -pob (Fig. 4), 1 Multico cabl, 6-pol, 1,5 long ssbling th xpint 1. Connct th 6.3-V input nd of th fin ba tub to th 6.3-V outlt of th DC pow supply.. Shot-cicuit th positiv pol of th 50-V outlt of th DC pow supply with th ngativ pol of th 500-V outlt and connct with th sockt - of th fin ba tub (cathod). 3. Connct th sockt + of th fin ba tub (anod) with th positiv pol of th 500-V outlt, th sockt W (Whnltcylind) with th ngativ pol of th 50-V outlt. 4. In od to asu th acclation potntial connct th voltt (asuing ang 300 V ) to th 500-V outlt. 5. Shot th dflction plats of th fin ba tub to th anod. 6. Connct th DC pow supply and at (asuing ang 3 ) in sis with th Hlholtz coils. - - CERN Tachs Lab

3 Fin a Tub Expintal pocdu 1. Pow up th DC pow supply and st acclation potntial 300 V. Thionic ission stats aft waing up fo a fw inuts.. Optiiz focusing of th lcton ba by vaying th voltag at th Whnlt-cylind fo 0 10 V until it lads to a naow, wll dfind ba with cla dg dfinition. 3. Connct th DC pow supply of th Hlholtz coils and look fo cunt I, at which th lcton ba is dflctd into a closd obit. 4. Mov th lft slid of th asuing dvic so that its inn dg, io iag and scap aptu of th lcton ba co to lay on on lin of sight. 5. St th ight slid fo both insid dgs to hav a distanc of 8 c. 6. Sight th insid dg of th ight slid, align it with its io iag and adjust th coil cunt I until th lcton ba uns tangntially along th slid dg coving th io iag If th lcton bas aft laving th anod is dflctd to th wong (lft) sid: 1. disconnct both pow supplis.. xchang th connctions at th DC pow supply in od to chang th polaization of th agntic fild. If th lctons do not ov on a closd obit but on a hlical cuv lin: 1. Loosn th ounting bolts of both holding backts (ad th infoation anual fo th fin ba tub).. Cafully otat th fin ba tub aound its longitudinal axis, until th lcton ba uns on a closd cicula obit. 3. Fastn ounting bolts. Safty pcautions Don t touch fin ba tub and cabls duing opation, voltags of 300 V a usd in this xpint! Do not xt chanical foc on th tub, dang of iplosions!! CERN Tachs Lab

4 Fin a Tub CERN Tachs Lab Classical xpints 1. uild up th xpintal stup (s stup ), fist without Hlholtz coils and obsv th ba insid th tub!. Magntic dflction of th lcton ba can b donstatd by appoaching th pol of a ba agnt to th cathod ay tub. 3. Now add th Hlholtz coils to th xpintal stup and pat. with th agntic fild of th coils! djust th agntic fild so that th obit of th lcton ba is copltly insid th tub! 4. Dtin th spcific chag / of lctons! To dtin th spcific chag / you asu th adius of th cicula lcton ba in a agntic fild. Th cntiptal foc at th obit is qual to th Lontz foc: v v v Th lctons w acclatd by th voltag btwn anod and cathod. That s whz w can calculat th spd of th lctons via th kintic ngy: kin v v E 1 pplying this in th fist quation you gt an xpssion fo / that only contains th paats, and that can asily b asud at th fin ba tub.

5 Fin a Tub Cycloton Tasks: 1. Gnat an lcton ba in th fin ba tub and adjust th agntic fild so that th obit is copltly insid th tub!. In which way dos th adius of th obit chang if you incas th acclation voltag (constant agntic fild)? 3. Masu th adius of th obit at a agntic fild of 0,0015T fo sval acclation voltags! 4. Copa to thotical valus! Rsults: 1. Sinc Lontz foc always act vtical to th oving diction, th lctons go on a cicula path. That ans it is possibl to foc paticl to fly an obit with lctic filds which is usd at cicula acclations, s blow.. Th cntiptal foc at th obit is qual to th Lontz foc: v v q q v If th acclation voltag incass, th lctons gt o kintic ngy, thi spd v incass as wll. caus of th popotionality of and v th adius aiss, too. 3. Th high th acclation voltag, th bigg is th adius of th obit (s.). 4. Calculation of th thotical valus with v q high low CERN Tachs Lab

6 Fin a Tub Paticl physics: cicula acclatos With ising ngy of th acclatd paticls LINCs (lina acclatos, s xpint cathod ay tub ) gt vy long and xpnsiv. That s why th ida of cicula acclatos was bon: by using agntic filds to foc paticls into an obit, th sa acclating unit can b usd ultipl tis. Th fist typ of cicula acclatos v built was th cycloton. Th acclation taks placs btwn two D-shapd lctods (so-calld Ds) by a high fquncy C voltag. stong agntic fild all ov th Ds focs th paticls onto an obit so that th acclation btwn th Ds can tak plac ultipl tis. ft ach sicicl paticls a acclatd by th lctic fild btwn th Ds. Lik w saw in task, th adius of th obit incass with high paticl spd. Sinc paticls w acclatd in th cycloton ach sicicl, th obit thy go is a hlix that s why high ngy cyclotons gt vy lag. Paticl souc DEEs Magntic fild Magntic fild Dflction lctod a ~ High fquncy gnato CERN Tachs Lab

7 Fin a Tub Synchoton Tasks: 1. St th acclation voltag to 00V. Rgulaiz th agntic fild thus th adius of th cicula path is 4 c!. Gadually incas th acclation voltag in stps of 5 V. Rgulaiz th agntic fild always that th adius is constant 4 c! Which fild stngth is ndd vy ti? 3. Copa to calculatd valus! Rsults: 1. s stup. To balanc th bigg adius, th agntic fild has to b incasd. 3. Sinc Lontz foc quals cntiptal foc, w can dissolv: v q v v q This xpint with th fin ba tub showd us: it is possibl to kp th adius of th obit constant by incasing th agntic fild synchonously to th ngy of th paticls. This is usd in cicula acclatos calld synchotons to kp th paticls on a stationay cicl (oppositional to th hlix path insid a cycloton). Th advantag of a synchoton is that th agntic fild nds only b at th path and not th whol sufac of th acclato that s why you can build up vy big xpints, till th 7 k long Lag Hadon Collid at CERN CERN Tachs Lab

8 Fin a Tub Paticl dtctos: dtination of ipuls and chag Tasks: 1. s a ba agnt to show that th ba in th fin ba tub consists of ngativ chagd paticls!. Choos any dsid acclation voltag btwn V and gulaiz th agntic fild thus th lcton ba is insid th glass tub. Masu th adius of th lcton obit and us this to calculat th ipuls of th paticls! 3. Copa you sult to th valu of th ipuls which can b calculatd of th acclation voltag! Rsults: 1. ppoaching th noth pol of a ba agnt fo bhind to th fin ba, th fild gos fowads to th obsv. Sinc paticls fly to th ight, th lft-hand-ul (valid fo ngativ chagd paticls) says that th is a Lontz foc on top. caus paticls in th fin ba tub a dflctd to th top, thy a chagd ngativly which dosn t wond bcaus thy a lctons. This pincipl is usd in paticl dtctos as wll: fo dciding if th chag of a paticl is ngativ o positiv, you obsv th tajctoy within a agntic fild. t CMS dtcto, th tajctoy is asud by th tack, ad of siconducto atials. Silicon tack in th iddl of th CMS dtcto CERN Tachs Lab

9 Fin a Tub. t th cicula path, cntiptal and Lontz foc a qual: v q v q v p caus th chag of th lcton q is known and agntic fild and adius can b asud, w can calculat th ipuls of th lctons. In paticl dtctos th dflction within agntic filds is usd to dtin th ipuls of paticls in th sa way as in th fin ba tub. That s why paticl dtctos nd stong agntic filds at th CMS dtctos this is a 13 long supconducting solnoid with a diat of 13. Th agntic fild at th axiu cunt of is about 4 T. Supconducting solnoid Myon dtctos Myon ndcap Tack Elctoagntic caloit Hadon caloit CMS-Dtkto 3. Passing th acclation voltag in th fin ba tub, th lctons gt th kintic ngy 1 v E kin. That s why th ipuls is: p v CERN Tachs Lab

10 Fin a Tub Paticl dtctos: dtination of ngy with caloits Tasks: 1. In which way do th lctons bco visibl at th fin ba tub?. Why do you nd to dakn th oo whn you us th fin ba tub? Rsults: 1. t th fin ba tub, th acclatd lctons hit atos of th filling gas and stiulat th to it light. Photon E Ionizing paticl Th sa pincipl is usd in dtctos: paticls which fly though spcial scintillating atial (.g. zinc sulfid) giv away thi kintic ngy to th scintillato, whos atos gt on a high ngy lvl. Dopping down to th initial condition, th ngy diffnc is ittd as a photon. This light can tansfod into an lctical signal by th photolctic ffct. Ionizing paticl Photoultipli Scintillatos ad of PbWO 4 (tanspant cystal) fo th EM caloit of th CMS dtcto Scintillato Fib optics CERN Tachs Lab

11 Fin a Tub. Th bightnss of th ba insid th fin ba tub is vy low and not visibl by daylight. Th bightnss of th light flash insid th scintillato is vy low as wll. Th flashs hav to b aplifid by a so calld photoultipli. Th photons ittd at th cathod a acclatd in an lctic fild btwn sval lctods ( dynods ). t vy dynod th initial photon causs th las of any sconday lctons, so th photo cunt is aplifid by facto That is sufficint to b gistd with lctic asunt aplifis. Dynods Piay lcton nod Signal Light Cathod Paticl physics: caloit Caloits a usd to asu th ngy of paticls. Thy a build up in lays: dns atial such as ion o lad altnat to scintillatos. Though intactions with th dns atial th piay paticls (whos ngy has to b asud) dcay in any sconday paticls which dcay futh until th piay ngy is gon. Th ngy is popotional to th ittd light in th scintillatos and th dpth of pntation. Scintillatos bsobs Fib optics Photoultipli CERN Tachs Lab