,fv \/Li."YL14UD TANK OPENING FEBRUARY 2nd, 1976 - No.I. The main reason for going in the t:mk was to find out why Chain 2 had been behaving irregularly: charging current had been fluctuating, and disturbance was both heard on the audio (bang) ampli fier and seen on the N~lIt. The effect did not always occur, but would start up eventually if Chain 2 \'ias left running; in the end the chain was 1eft off and the machine ran on Chains 1 and 3 very satisfactorily at acondi tioned voltage of 13.6 r-W. Because demand on the l4UD was reduced by the AINSE conference it was decided to schedule a tank opening, attend to Chain 2, CUlTY out a complete point change, do other work, and have work done in parallel 1nthe source room on LevelS. ' *************** The first effort in the tank was to examine the entire charging system. Chains 1 and 3 had stretchE;d by about the same amount as was found on the first opening after the ne\'i chains were fitted. Chain 2 had stretched some bit less because it had been off for most qf the running time. The pulleys of all chains were out of contact with the oiling pads when the motors were at rest and, clearly, no oiling had been taking place for some time; correspondingly it has to be remembered that the performance of chains Land 3 had been excellent. We ran the motors and Nos. 1 and 3 "bottomed". There ''ias. no undue noise from any chain, uordid there appear to be unusually high wobble on either the ascending or descending half of any chain. Before carrying out any work we did a charging test at 2; 4; 6 and 8 kV. There was no onset sparking until 6 kV, though in the chase of Chain 1, there was a weak spark low on the negative inductor at a lower voltage. Within the ,usual limits all chains behaved the same. The felt oiling pads were cut about by the new shimstock rims, even though the pads had been modified in such a way that we had believed they 'vould not touch the rims, and would both survive and be effective. There was a general matted fuzz on all pads. The ne,v chains appeared to be in good condition and had generally retained their original plated appearance, though, pellets were pitted by spark damage at the rims. There was no evidence of hardening, cracking or other damage to the blue nylon pulley rims, either below or in the terminaL It was decided to remove, and leave out for this opening, all three oiler pads together with their supports, however, the three pUlley rims were to be oiled in as close as possible to the usual way before final test and button-up~ . The chain's seemed to be somewhat twisted: Le. the pellet rivets \vere not parallel to the plane of the rim of the .pulley. It was believed that, when No.1 terminal pulley, and No. 3 motor pulley were taken out early in December (to attend to the bearing wear \vhich gave rise to finely divided steel powder) they were replaced out·of correct alignment. All 3 chains were removed; top and bottom pulleys were realigned with plumb bobs. Two pellets were taken out of chains 1 and 3; none were taken out of chain 2. During the procedure the mounting bolts for the bearing of the terminal pulley of chain 2 were found to be loose, and clearly had been loose since l~st adjustments. - 2 - .', Anidlerb~lont:;iTl9'tochain 3 ina ccasting about halfway up the HiE. COl11lTIn. had a .1~I'gepiece.,broken off, it. This idler, and'.2 others' betlvecn the t,cl:minal';and,H,cE.basewer6,replaced. Inthc,tetmin'llall c. icllcrs(thc terJilinal·,•.tdlers \·lith,d ~c . poor"contact, .ifanyat all. ,Whena:dj usting the supports of these idlers in order to present their rims and contact springs in the correct aspect· to the pellets it ,,,a5 found that theelongatecl.brack.et holes in the idler supports werematginal1y tight.foraIl chains but just that much tjghtcr forchain2ancl.consequ.clltly the brack.ets"forNo. 2wereremovedan.d machined toallowadequate·adjustmre'I'tt. Thedownd.c. idler of chain 2 had only Lcontact spring and anew idler was £i1;"1:;,ed.; the ..upicller of chain 1 was in poor conditi.on and also was renmved. \Vhen,the' He'" chain.s\\';e.ne~in, and.ali,gned, .all castll}gidler.sWc.r.e examined ;.q.gClin and adjusted wh·ere necessary .. Because we. felt that a good t'btlsi'cstal't"·hadtobeTll<.tde, verycare'fulattentionwaspaidtoallchains, idlers,' inductors and chain tension. . The inductors were set withespecial'carc; possibly the greatest attention yet; waspp.id to syrrmetry the, chains in the indyctors an- dthe, clc?re1 to Hlhch( the straight paJt of the lncl.uctorwaspara lleltothecha1.n,.allowl l1 gtheflare' to ,take care of itself. This statement relat.esto both terminal and driving inductors. ?I The. rims. of the motorpulleys were t0tlch~d with a Kimwipe wet wiUrtr Cll1s former oil'vhile thepulleyswoEeturnedfoF onc or two rev(jlutions;"then't~c' pulleys were turned for at least one revolution of the chain (14 pulley turns) and the rims were arbitrarily "dried" until rims and chains seemed to have the correct oilfi1rnon them. No extra oil waspllt.on to compensate £OT theremov~l ;, of the oiler pads . The pre-button up charging tests seemed to go as usual for -.a113 chains. POINTS: . A comIJlete set of points , column. and tube, had arrived from NEC prior to tllctank opening Clndwewerecopfronted, ,.;ith, t.he situation that tube points were needing to be changed at each opening ("hiTe column points remained steadfastly in excellent condition,thol.lghslowlygetting just that much duller with every interval. Tactics, rather than necessity, calledforachange.oLall points ,especially when one c()nside:rs that most rings in eachuni thavetQ; be . removed to ch.angeal1.tybepoint5 ,therebypresent;ingan ideal situati()nfor '. ( chmlgingcoll.lmn points as 'veIl. Because' so many rings would be taken off in all units a thorough cleaning of the column \'louldbe facilitated. Only 1 point ,iu,the macl"1ine needed.tobe.:replaced in terms of the uSual crit.eria; this was a .Type 3 point at 26/2/3 (Unit 26, 'Lube 2, Point 3 in the order seen by a particle travelling along the 1;ube). All points ,,"ere removed and the ones newly received from NEC <\vereputin. It was noted wryly that some of these ne\\' points had, . instead of the conventional Screws, the same star-headed versions which had evoked so much amusement before. them; Tube/column stringers were fitted totheS units still remaining\dthout hence the entire column now h as stringer5. Black dust in the vicinity of the coupling between the 1O\'J er shaft and its main alternator led to the discov~rY that the rubberycoupling,iwasa,lmost completelY sheared. Having' no replacement a different type was ,fitted arid. Cln adaptor made to accommodate it. - 3 -, The alternator bearing in the 5 MeV casting was very noisy, and was replaced. Three more r.f. straps were fitted from the top of the column to the roof of the tank; there are now 8 of these around the t.op of the column. They are .copper strip, 3 inches wide and about 16 gauge. Quite a few of the AND Type 1 shorting rod rollers had seized up, though because of their shape, the rods contact them and pass easily. The Type 2 dev~ces being tested are in perfect condition. The 3 nylon tubes which had been fitted "in parallel" with each other from the terminal to the 17 MeV casting, for the purpose of observing. their behaviour under SF6 and high voltage, appeared to be in perfect condition. They were taken out, pressurized to 80 psi, and immersed in water for more sensitive detection of leaks; no leaks were observed at all. It is likely that the "on-off" type control rods (i.e. the ones which do not perform continuously variable functions, such as lens control, or sublimer variac control), will be replaced by pneumatic devices of the tYJ)e which has operated the /\NU design foil changer perfectly for a number of years in the EN. . The midsection pump was opened. One sublimer was \vrecked and the other unused; the wrecked one was replaced.- TheNEC ionizer was taken out of the pump permanently as. it has not been l,lsed since the 10 9Js pump was fitted in the midsection. Series resistors were fitted to limit currentdrmmby the pump. The metering fault was found to be due to a short imposed by a shielding box too closely fitted. The box was omitted for the time being. Sublimers in both terminal pumps were changed manually. Pyrotenax, which was installed some months ago, was meggered and found .to be 15-20 megohms; it road about megohms at last opening but was not meggeredinits "unused"state at installation. The rear of the foil changer was opened and the foils checked. About 80% of the sample examined were broken; also the beam spot was slightly higher, and to the left, (for a vertical foil) than appeared before. The spacer fitted earlier to correct for the error in length of the then new NEC foil holders was taken out and a tapered spacer fitted to correct additionally for the offset beam pattern on the foils. Three groups of foils were loaded: one group \-Jas 5 micrograms and another 2-3 micrograms. Two batches of calfad ion were tried. . ,raP and bottom or every casting was cleaned with a vacuum cleaner. Every 'i,lni;t. oJ shaft Wi:lS \-Jipcd vigorously with a dry Kimwipe and this removed the 'cius'ty'dlscol'ouratlon which had been accumUlating steadily. Tests on a silOrt sectiono~!l9raf:t, using oral fluid, established that the film on the perspex responded readily to this solvent. The section was dried by particularly vigorous rubbing and no more of the shaft was treated, partly because the basic constituent of the solvent is undesirable in the machine and partly because of low availability of the solvent in quantity. Each ring was checked carefully for looseness on the posts and several adjustments \-Jere made to screws. We continue to feel that real damage can occur easily to post fittings on which the rings clip and full examination, however tedious, is mandatory in regard to safe ring connections .. - 'I .' ;,'. l Th.e positions were determined: one for the existing source and one for the' Sputte.rcone source which istobe installed shortly; The magnet was Totated a nymberoftimes and reproducibility was very good. Full alignment of the present source was carried out. Before the source beam line was closed up a crosspiece was fitted to the rear of the inflection magnet: the straight through end wilTev€mtually carry a viewing port: and the other two ends the 21.,/s pump and a valve with fitting for.leak chasing head. ****************** .,.~#teTgassing .. upall.,valtage·and tube and · column mete, r,'l'n.g appe·a,r.ed 'no·r.ma(r·• , there w;.ts I i ttle trouble in reaching 11 MVi. However ,notlbng .,after theexperimen.ters began to.usethe machil1.eit be,came c~ear that the Chain 2 trouble had not been cured . Breakdownnoise cmild ·behc,:l.rd on the audio (bang) amp-lifierandseen at the same time on the NHR; likei'lise the same metering effects were there~ For a time \I/e believed the fault might occur when Chain 2 and at least one of the other motors \I/ere run together because the way the motors drop at start~p might belninging a high voltage lead .near ground somewhere. We later ran Chain 2 on its own and i t worked well :with 23 kV inductor vol ts for about 20 minutes, then the effect began again; This disposed of thetwo"motoridea and we assume that chain str.etch ,is a likely cause. c.c. Professor Newton Dr. Ophel T.A. Brinkley Dr. Weisser 16th February. 1976; Dr. Rathmell, N.E.C. Chiaki Kobayashi, JapanJ\tomic Energy Res. Inst. Dr. J . Ball , OakRidge. Dr. l<:1tnri, TokyollnivcTsity. •