The never-ending story of the BaBar RPCs

-GT improvements-Production status and schedule-Motivation for additional request-Belt project

-The 17/18 layer story

-Remediation status (a bit of hope)

-Summer installation: a preview

Production technology improvements

http://www.pd.infn.it/CSN1/riunioni/18-12-2001/morganti_rel_rpc.pdf

Circuito di oliatura

Sala assemblaggio

Certificazione olio di semi di lino

Controlli di qualita’ in assemblaggio gap

Controlli di qualita’ in volumi di gas

Tutto questo e’ un salto culturale, sopratutto per GeneralTecnica, di estrema importanza

Cornici preforate

Final certification

Production status (gap TB/M)GAP (TOP/BOTTOM + Middle)

fatte (totale incluso scarti) = 183scarti (cozze) = 11 (le cozze sono state usate come camere sacrificali)scarti recuperabili (leakage) = 2

totale gap usabili (incluso leakage) = 172

totale gap testate (QC/QA) = 172-26(*)-27 (**) = 119(*) = da oliare(**)= da sigillare

GAP da costruire = 47 (19 T/B + 28 M)

Production status (envelopes TB/M)ENVELOPES TOP/BOTTOM

envelopes assemblati: 40 (12 FT19 + 28 FT02)envelopes testati con i cosmici: 36 (8 FT19 + 28 FT02)envelopes spediti : 12+10 =22pronti per la spedizione = 10

ENVELOPES MIDDLE

none

Envelopes da assemblare = 69

Production status (belt)BELT

belt assemblati: none

Belt da fare: 24

Camere da costruire e assemblare = 24

ScheduleGap

giorni lavorativi a GT ancora allocati a BaBar = 30max 2 gap/day = 60 gap.

GAP da costruire = 71 (19 T/B + 28 M+ 24 Belt)

Envelopes

considerando 1 envelopes/day e 71 envelopes da fare la produzionenon finisce prima della settimana del primo maggio

Ulteriori richieste

Si capisce quanti progressi siano stati fatti nella produzione industriale degli RPC. Questo non e’ avvenuto a costo zero per BaBar dato che molte delle prove sono state fatte utilizzando il finanziamento ricevutoper la costruzione del FECap ritenendo funzionale al progetto lo svolgimento di alcuni test non previsti in fase iniziale. C’e’ stato cioe’ un veloce R&D strettamente finalizzato al miglioramento delle procedure costruttive.

Quindi: overspending, necessita’ del trasporto per via aerea, valutazionedel numero di spares, inclusione della Belt nel progetto, un acquisto di ulteriori cavi segnale funzionale alla schedula stretta di installazione e infine un primo intervento sul barrel necessario per la ‘remediation’.

Il progetto Belt• Design criteria

– Leave gap accessible– Be easily removable– RPCs narrower than envelope, so that the 2 layers

can be offset in Z and the buttons are not aligned– Minimum number of RPC sizes

• 2 sizes– Large

• Belt positions 2,3, & 5• Need 12 + spares• Position 5 chambers require HV, DAQ, and Gas lines 2

m longer than the others. Extensions?

– Small• Belt positions 1 & 4• Need 8 + spares

• Possible future improvements– Preliminary studies on belt under the forward door

using either of 2 sizes

5

4

32

1

This area is used to get the wires, cables and tubing to the racks

In conclusione: 4 camere * 5 lati+ 4 camere (sotto o spares)

Belt physics motivation

Ageing - Young chambersA Novembre 2000 sono state installate 12 camere (24 moduli) nelForward End Cap. Esse sono operative da Gennaio 2001. Possiamo quindi caratterizzarne il funzionamento dopo un annodi run.Queste camere hanno ‘poco’ olio, la sua superficie e’ perfettamentepolimerizzata e le analisi chimiche non hanno rilevato tracce dicontaminanti.

Il loro comportamento e’ piuttosto istruttivo. Esse appartengono a trecategorie;a) 20 moduli a bassa esposizione (frazioni di Hz/cm2)b) 2 moduli a media esposizione (1 Hz/cm2)c) 2 moduli ad alta esposizione (5 Hz/cm2 )

Erano tutte uguali a t=0, circa 0.5A/m2 di dark current in plateau

Ageing - Young chambersA Novembre 2000 sono state installate 12 camere (24 moduli) nelForward End Cap. Esse sono operative da Gennaio 2001. Possiamo quindi caratterizzarne il funzionamento dopo un annodi run.Queste camere hanno ‘poco’ olio, la superficie e’ perfettamentepolimerizzata e le analisi chimiche non hanno rilevato tracce dicontaminanti.

Il loro comportamento e’ piuttosto istruttivo. Esse appartengono a trecategorie;a) 20 moduli a bassa esposizione (frazioni di Hz/cm2)b) 2 moduli a media esposizione (1 Hz/cm2)c) 2 moduli ad alta esposizione (5-10 Hz/cm2 )

Erano tutte uguali a t=0, circa 0.5A/m2 di dark current in plateau

Currents

The current drawn by the inner (blue) 20 modules has gone upto 200 A at the end of the year (with beam !). Green is 17+18.

It looks strictly proportional to time (integrated charge), it makes stilla tiny current (~ 4 A/m2) but……

Efficiencies (inner)

-1.4 %/year

-4.8 %/year

~-8 %/year

Rates (inner layer)

Rates for normal chambers 1-2 kHz/m2

seen in cosmic running

Quick evaluation for integrated charge:Q= rate*streamercharge*time ~ 5*103*10-9*3*107

~ 150 C/m2 (tragically small)

Rates (outer layers)

Outer chambers at ~15kHz/m2 in cosmic runningIncreased since the Beginning for layer 17,Started to decrease for Layer 18 in July (!?)

Rates (from beam background)

1 layer= 12modules

1 module ~ 2m2

Therefore:~200kHz/m2

in 18and ~50kHz/ m2

in 17

(we are working hard on understanding and fixing this by shielding)

Rates (from beam background)

1 layer = 12modules1 module ~ 2m2

Therefore:~150kHz/m2

in 18and ~25kHz/ m2

in 17

Actually layer 18 runs at the saturation limit

Given a resistivity~5 * 1011 cm, the streamer rate () is limited by the dropof voltage :V= 2 (d/S) * q *

No need for a measurement, the efficiencyin a collision run will be 0.

Evolution of efficiency (cosmics)

17

18

Feb19 Dec04

Visualization of the disease

17 18

18

Remediation

-very desirable both on short term (stop decreasing muon ID )

-and on long term (avoid barrel replacement, a real bloodshed)

-we followed many paths (see BaBar Coimbra talk from C. Lu)

-mostly driven by the prejudice that chemistry is wrong in our RPC

-got only temporary (though impressive) inversions of behaviour both with O2 and Ar flow (no HV applied)

-promising results with a combination of Ar and reverse (direct ?) HV (most of the work done at LNF, confirmed at SLAC and Princeton)

BTW (effect on -ID)

Tight selection

Loose selectionBaseline one year (2001)

MethodFflow pure Ar and apply a reverse voltage which makes the current go into the 200 A

region (HV ~ 5kV). Wait until Q~ 300C. Set back RPC conditions.

This is IFR047 before and after cure. It is a removed FECap chamber.

V

Time persistency

The recover of efficiency persists over a couple of month time.

A total of 10 chambers have shown somewhat a similar behaviour in lab

June 26 Dec 15

Visual inspection

Chemical analysis being done

A failed attempt on the field

We have run an attempt during X-mas vacation on a few barrel modulesmainly to understand the context and evaluate the difficulty and the needfor carrying on a mass remediation.

We have learned a lot but we have no meaningful results on the efficacity

In short: -half of the modules have shown gas flow problems

-> survey of the situation and prepare an intervention-most of the modules have shown a HV mismatch -> redo the entire distribution system-not enough (by far) charge given, no results to present now

We are preparing further tests, making use of the backward ECap mainly

Installazione

-a Marzo potremmo discutere lo sblocco del s.j. per l’installazione

-una schedula che tiene in conto la maggior parte delle attivita’ c’e’ (manca la parte del barrel [HV, gas , remediation])

I punti principali sono:

- Installazione 1 Luglio - 30 Ottobre- 2 turni per 5 giorni e 1 il sabato per il lavoro duro

e 1 semiturno di QA a seguire- contributo stimato di 24mu di personale tecnico

( da raffinare, 1 TM, 2EM, 3TE per 4 mesi) [US contribuisce con >30] Ingegneri e fisici da aggiunger

Crude task list

RPC installation

Overview of work items• Remove 5 layers of RPCs and replace with brass absorber• Replace all or part of the remaining 12 RPC layers underneath

the flux return steel.• Remove the existing layer 18 and replace with additional steel

absorber containing 2 slots, each fil led with 2 single gap RPCs.• Add belt RPCs around the circumference of the endcap.• Add new High Voltage distribution boxes• Add new gas distribution system• Cable the new RPCs to the minicrates• Expand cooling to Layer 18/19 and power supply racks.• Expand temperature monitoring

To add: redo distribution system on barrel improve on gas distribution and monitoring run a mass remediation if proven from test we are doing

Gory detailsInstallation order

The rough installation order will be:• Remove insulation, remove doors over lower flux bar gaps• Drain endcap water lines, remove water cooling loops• Disconnect LV, scalar, GMB, and AC lines to LV rack on top of

door• Remove layer 18 minicrates, HV boxes, and gas distribution

boxes.• Remove LV racks• Remove door platforms & upper flux bars• Disconnect RPC end of RPC to minicrate cables and dress on

rack. (top)• Disconnect minicrate end of RPC to minicrate cables and dress

on detector. (bottom)• Remove gas lines at RPC end (top)• Cut and remove HV lines at RPC end (top)• Cut and remove RPC to minicrate cables (vertical strips) at RPC

end (top)• Disconnect and remove Low Voltage wiring running from layer

18 to racks• Disconnect and dress to minicrate rack scalar cables running

from minicrate rack to DMUX boards in LV rack• Disconnect and remove DAQ cabling between layer 18

minicrates and FEE crates• Shut off AC power and remove AC line from Gleason to

minicrate and LV racks• Remove raceways connecting minicrate racks to detector.• Remove minicrate racks• Remove counterweights• Remove lower flux bars• Remove midplane raceways and cables.• Remove gas lines at RPC end (middle & bottom)• Cut and remove HV lines at RPC end (middle & bottom)

• Cut and remove RPC to minicrate cables (vertical strips) at RPCend (middle & bottom)

• Install temporary Gleason support & remove layer 18• Install layer 18/19 mounts• Install layer 18/19 top• Replace Gleason support• With the minicrate racks removed from IR2

• Modify layer 18 minicrates and install in new racklocations

• Relabel, reterminate, modify and reinstall RPC tominicrate cables

• Relocate LV supplies into rack• Relocate GMB/MUX crate into rack• Install LV and DAQ cables• Test and debug minicrates

1. Mount installation platforms and remove old chambers (bottom)2. Install absorber (bottom)3. Install new RPCs (bottom)4. Quick test of installed RPCs (bottom)5. Mount installation platforms and remove old chambers (middle)6. Install absorber (middle)7. Install new RPCs (middle)8. Quick test of installed RPCs (middle)9. Reinstall bottom flux bars10. Reinstall minicrate racks11. Install racks for HV and gas12. Install lower raceways and recable bottom half of detector.13. Connect gas and HV (bottom)14. Mount installation platforms and remove old chambers (top)15. Install absorber (top)16. Install new RPCs (top)17. Install upper raceways and recable upper half of detector.18. Connect gas and HV (middle and top)19. Final test of all inner installed RPCs20. Cosmic ray tests all inner installed RPCs

Gory details (cont.)• Replace upper flux return steel.• Replace cooling loops, insulation• Install layers 18,19 (bottom and middle)• Connect gas & HV layers 18,19• Connect DAQ cable layers 18,19• Final test of all layer 18/19 RPCs• Cosmic ray tests all layer 18/19 RPCs• Install belt absorber, RPC mounts• Install belt RPCs.• Cable and Connect Belt RPCs• Test belt RPCs• Cosmic ray commissioning of entire Forward Endcap

The key to maintaining schedule will be to do as many tasks inparallel as possible. Minicrates can be installed into the racks,connected to LV and the FEE crates, and tested after theracks have been removed from the detector and while thechambers are being installed.

Intensive manpower need !

Conclusioni

E’ dura, mi serve il vostro aiuto, ma ce la faremo.