Status of LAr TPC R&D (2) 214/Dc./23 Nutrino frontir workshop 214 Ryosuk Sasaki (Iwat U.)
Tabl of Contnts Dvlopmnt of gnrating lctric fild in LAr TPC Introduction - Gnrating strong lctric fild is on of ky R&D subjcts toward ralization of a larg scal LAr TPC Gnration of strong lctric fild - Mthods of gnrating lctric fild - HV gnrator - Undrstanding of charactrization using circuit simulation (LTspic) - Optimization of lmntary dvic modls - Rsults of circuit simulation Summary
Introduction Principl of LAr TPC TPC is stord insid th cryostat Th cryostat is filld with LAr filld with LAr 1. Chargd particls flying in LAr TPC Anod 2. Flying particls racts with LAr in TPC, th ionization lctrons ar gnratd 3. Ionizing lctrons undr th forc of th lctric fild, drift to th anod sid 4. Th anod is dividd into a grid-lik, obtains th position information of th gnratd ionization lctrons in two dimnsions (x, y) 5. And obtaining position information of th z- dirction from th tim it took to drift to th anod from th gnration position z Chargd particls Cathod x y Drift Ionization lctrons Elctric fild 6. Th track of flying particls can b rproducd in a thr-dimnsional
Agndas to gnrating lctric fild Whn lctric fild is wak, ionization lctrons can b capturd by impuritis bfor raching th anod Mor than v=1.6mm/msc rquird Mor than E=5V/cm rquird 1. 2. Anod Whn lctric fild is non-uniform, a mismatch btwn radout and gnratd position can happn Anod Cathod Wak lctric fild Cathod Elctric fild Agndas: 1. Gnration of strong lctric fild (Mor than 5V/cm) 2. Uniformity of lctric fild Today's discussion is about this. R&D on fundamntal tchnology of HV using a small LAr dtctor (drift lngth 1cm)
Configuration of TPC Fild Shapr placd btwn th cathod - anod for th uniformity of th lctric fild in th prototyp (drift lngth 1cm) in dvlopmnt. Also, it sts out 5V/cm by supplying voltag to lctrod (in th figur). Anod V AG, FS1 1kV FS2 1.5kV FS3 2kV FS4 2.5kV FS5 3kV FS6 3.5kV FS7 4kV FS8 4.5kV FS9 5kV FS1 5.5kV Cathod 6kV radout rgion 64mm 1mm 15mm 11mm Drift lngth 1mm y x 11mm z
Gnration of strong lctric fild Two possibl mthods of gnrating strong lctric fild 1. Supplying HV from th outsid of th cryostat through th fdthrough 2. Gnrating HV within th cryostat (filld in LAr) Whn LAr TPC coms to b a larg siz (drift lngth svral tns m), it's ncssary to supply a voltag of svral MV for gnrating lctric fild of 5V/cm It s difficult to supply from th outsid of th cryostat by brakdown limit of fdthrough in MV supply W adopt option 2: Considr th Cockcroft-Walton(CW) circuit as th dvic
Fatur Cockcroft-Walton(CW) circuit This circuit gnrats a high DC voltag from a low voltag AC Circuit that combins a capacitor and diod Vout = 2Vin (Numbr of stags) Sinc it can b output from ach stag, it s compatibl with TPC structur AC sourc Each capacitor is chargd, th sam rol as th powr supply Half cycl Half cycl 2V P-5
Dsignd a CW circuit Dsignd a 1-stag CW circuit for supplying HV in th prototyp: Protction circuit for AC sourc Discharg protction circuit Vin Vdc (AG,FS1) V1 (FS2) V2 (FS3) V3 (FS4) V4 (FS5) V5 (FS6) V6 (FS7) V7 (FS8) V8 (FS9) V9 (FS1) V1 (Cathod) Undrstanding of CW circuit using circuit simulation (LTspic): W will compar with an actual masurmnt in nxt stp. Circuit simulation is carrid out by simulating th actual oprating tmpratur (-186 dg C) Important to us actual proprtis of ach lmntary dvics at th low tmpratur W masurd th low tmpratur proprtis(-196 dg C), and thn crat and optimiz lmntary dvic modl in simulation
Masurmnt proprtis of lmntary dvic (Capacitor) Masur th low tmpratur proprtis of th capacitor by LCR mtr filld with LN2(-196 dg C) put a capacitor in th sockt put in a containr Capacitor PHE45 (EVOX RIFA) LCR mtr (HP 4275A) Masurmnt rsults (-196 dg C) sampl_1 sampl_2 sampl_3 sampl_4 sampl_5 Avrag 33.63 33.4 33. 33.32 33. 33.27 Masurmnt rsult at room tmpratur(2 dg C) is 32.47nF(avrag) According to masurmnt rsults, crat a lmntary dvic modl as th capacitanc is 33.27nF
forward currnt [ma] rvrs currnt [pa] Masurmnt proprtis of lmntary dvic (Diod) Masur th low tmpratur proprtis of th diod by micro-ammtr filld with LN2(-196 dg C) put a diod in th sockt PC put in a containr Diod rgp2-2 (VISHAY) 2 15 1 5 Forward charactristic 2 dg C -196 dg C 1 2 Applid voltag [V] Micro-ammtr (ADVANTEST R834) Rvrs charactristic Crat a modl of diod to rproduc th masurd rsults Making a comparison btwn th cratd modl and masurmnt rsults in th nxt slid -5-1 -15-2 -25 2 dg C -196 dg C 2 4 6 8 Applid voltag [V]
rvrs currnt [pa] forward currnt [ma] Optimization of dvic modls 2 Masurmnt rsults(-196 dg C) 2mA Cratd modl 15 Forward voltag drop Vf = 2.3 V 15mA Forward voltag drop Vf 1.95 V 1 5 Sris rsistanc Rs = 9.68 Ω 1mA 5mA Sris rsistanc Rs = 9.89 Ω -5-1 -15-2 -25 1 2 Applid voltag [V] Saturation currnt Is = 1pA Whn Vin=8V I = 2pA 2 4 6 8 Applid voltag [V] -5pA -1pA -15pA -2pA -25pA 1V 2V Saturation currnt Is = 1pA Whn Vin=8V I = 2pA 2V 4V 6V Th succssful cration of a modl that low-tmpratur charactristics match Charactrization by circuit simulation 8V
Output voltag [V] 1- (Th gnratd voltag) / (Th gnratd voltag at first stag) [%] 8 7 6 5 4 3 2 1 Rsults of circuit simulation (LTspic) Input voltag vs output voltag 45 9 135 18 225 27 Input voltag (Vin) [V] N=1 N=2 N=3 N=4 N=5 N=6 N=7 N=8 N=9 N=1 -.2 -.4 -.6 -.8-1 -1.2-1.4-1.6 Th ratio of th gnratd voltag of ach stag to on of first stag 1 2 3 4 5 6 7 8 9 1 Numbr of stag (N) Thr is -1.6% of discrpancy of voltag at 1th stag compard with first stag - A larg influnc of dvic charactristics in lowr stag - Sinc th dvic is incrasd along with th incras of th numbr of stags, th output voltag bcoms non-linar W will compar with actual masurmnt in nxt stp Vin=18V
Summary Dvlopmnt of gnrating lctric fild in LAr TPC Gnrating lctric fild is on of ky R&D subjcts toward ralization of a larg scal LAr TPC Agndas: 1. Gnration of strong lctric fild W ar dvloping CW circuit HV gnrator Circuit simulation basd on actual masurmnt of th lmntary dvic proprtis at th low tmp. is dvlopd W will compar with actual masurmnt 2. Uniformity of lctric fild Undrstanding with simulation softwar(comsol) is in progrss Plan to study with cosmic ray masurmnt