10 picoseconds original design goal(light travels 3mm in 10 psec!)gives large factor of background rejection;phased plan, start with 20 ps (<2 year timescale),need better than 10 ps for full machine luminosity (<4 years)

Use time difference between protons to measure z-vertex and compare with tracking z-vertexmeasured with silicon detector

Pileup Background Rejection

Ex: Two protons from one interaction and two b-jets from another

Test Beam Studies for FP420 Fast Timing

WHO?Developers: UTA (Brandt), Louvain, Alberta, FNAL

WHY?

How?

How Fast?Picosecond WorkshopOctober 16, 2008IPNL, Lyon

TB shifters: UTA, UC-London, Louvain, Prague

Fast Timing Is Hard!

• 3 mm =10 ps• Detector• Phototube• Electronics• Reference timing• Rad Hardness of detector, phototube and

electronics, where to put electronics in tunnel• Lifetime and recovery time of tube, grounding• Background in detector and MCP• Multiple proton timing

ISSUES Time resolution for the full detector system:1. Intrinsec detector time resolution2. Jitter in PMT's3. Electronics (AMP/CFD/TDC)

FP420 Baseline Plan1 GASTOF 2 QUARTICs

Lots of 3D siliconTwo types of Cerenkov detector are employed:

GASTOF – a gas Cerenkov detector that makes a single measurement

QUARTIC – two QUARTIC detectors each with 4 rows of 8 fused silica bar allowing up to a 4-fold improvement over the single bar resolution

Both detectors use Micro Channel Plate PMTs (MCP-PMTs)

The Detectors : 1) GASTOF(Louvain)

Not so much light since use gas,but full Cerenkov cone is captured.Simulations show yield of about 10 pe accepted withinfew ps! 1 measurement of ~10 ps

4x8 array of 6 mm2 fused silica bars

The Detectors : 2) QUARTIC

UTA, Alberta, FNAL

Only need 40 ps measurement if you can do it 16 times (2 detectors with 8 bars each)!

proton

phot

ons

First TB Results ( Fall 2006)

<70 psec/Gastof (Burle 25 um 8x8 tube, 4 pixels)>90% efficiency, dominated by CFD resolution (used Ortec 934)

G1-G2 For QUARTIC bar 110 psec Efficiency 50-60%

For events with a few bars on see anticipated√N dependence

March 2007 Test Beam

(t)=45 ps (t)=35 ps

Threshhold discrimination CFD algo simulatedQUARTIC 80 ps/bar (15 mm bar) 80% efficient

if G1=G2 then t=25 ps each, but G1 has faster tube (Hamamatsu 6 m pore vs 25 m Burle) and better mirror; extract resolution G1=13 ps G2=32 ps, initial estimate 80% efficient

Latest QUARTIC Prototype

Testing long bars 90 mm (HE to HH) and mini bars 15 mm (HA to HD) Long bars more light from total internal reflection vs. losses from reflection in air light guide, but more time dispersion due to n()

HE

HH

HC

QUARTIC 15 mm bar/75 mm guide

20 ps

20 ps

~ 5 pe’s accepted in 40 ps

QUARTIC 90 mm bar/0 mm guide

40 ps

40 ps

40 ps

~ 10 pe’s accepted in 40 ps

June 2008 Test Beam

• In between Mar 2007 and June 2008 had two largely unsuccessful test beams due primarily to tracking failures; for the June run we planned to be secondary user for first week with 3dsil group, and primary user for 2nd week, in order to ensure good tracking

• Planned laser tests at Louvain prior to TB run; mixed success

• Planned to have fully functional analysis program, mixed success

• Main goals of June run to validate detector design, including using tracking for efficiency measurement

Electronics

MCP-PMT Preamplifier SMA

LCFD Fast Scope

SMA

SMA Lemo

Fast Scope

For GASTOFreplace CFD/TDCwith single photon counter

QUARTIC:Photonis Planacon10 m pore 8x8Gastof:Hamamatsu 6 m pore single channel or equivalent Photek

Mini-circuits ZX606 GHZ or equivalent

Louvain Custom CFD (LCFD)

HPTDC board(Alberta) interfaces to ATLAS Rod

(a) Experiment channel

(b) or (c) TB channel

LCFD

Luc Bonnet(Louvain) tuned LCFD mini-moduleto Burle planacon;12 channel NIM unit

June 2008 Test Beam Setup

trigger paddles3d-sil+Bonn telescopefast timingCerenkov

comment onalignment

FP420 Timing Setup

G1G2

Q1

Amplifiers

Data Acquisition

• Lecroy 8620A 6 GHz 20 Gs (UTA) • Lecroy 7300A 3 GHz 20/10 Gs (Louvain)• Remotely operated from control room using TightVNC• Transfer data periodically with external USB drive

UTA funding from DOE ADR grant and Texas ARP grant

Good Trigger is ImportantSpray event add veto

Coherent Noise!

channels in adjacent rows

Good Event

5 ns/major division

Online Screen Capture

one histo is 10 psper bin others are 20 ps

histogramdelta timebetweenchannels

FWHM<100so /2.36 ->dt~40 ps

Offline Analysis

• Too cumbersome, not getting results in timely manner• I implement streamlined approach + round the clock analysis

shifts (one data taking shifter, one analysis shifter: Nicolas, Vlasta, Shane)

-start with basics -plot pulses -pulse heights -low threshold cut -raw times -time differences -add tracking later

overflow -> switch from 100 to 200 mv scale

acceptance

Determining Pulse Time

Burle (HF)

Hamamatsu(G1)

LCFD (HFc)

Linear fit, use 50% time

Dt

QUARTIC Long Bars after LCFD

56.6/1.4=40 ps/bar including CFD!

Time difference between two 9 cm quartz bars after constant fraction discriminationis 56 ps, implies a single bar resolution of 40 ps

LCFD Resolution

Split signal, take difference of raw time and CFD time-> LCFD resolution <27 psThis implies detector+tube ~30 ps

Tracking /Scope Synchronization

6mm

All tracks

HEc On

Early tracking results:

• 88% of tracks 170<x<260 have HEc bar on • 98% have HF on (lower threshold)• Timing does not seem to depend on whether or not there is a track (efficiency is high)-> can use all non-tracking data

HF Efficiency

6 mm

fraction ofevents withgood trackand HF bar on as a functionof track position

GASTOF On

GASTOF Displaced 19 mm

All tracks

dip ~1 mmwide

Multiple scatteringeffects in 400 um wide, 30 cm long stainless steel edge of GASTOF (cause veto)!1mm depletion impliestracking projection issues, detector tilted slightly, or both

edge

See Schul talkfor more details

What to Measure: QUARTIC

• Data taking still in progress (lost a graduate student)

• Dependence of efficiency, pulse height, time resolution on bar type and position, HV, 0 vs 1 vs 2 amps, as f(scope resolution 50 vs 100 ps, 3 vs 6 ghz)

• Before and after shift in veto counter• Also have some 25 m tube data • ``Time track’’ using all channels

QUARTIC vs GASTOF

• Do we need both?• G one (or two) measurements 10-20 ps need to figure out readout integration• Q multiple measurements 40 ps each 10-20 ps overall, some multi-proton capability,

integration into readout through HPTDC, need to demonstrate N improvement of 8 bars• Different background characteristics• I think answer is still yes

Summary

• June TB two+ weeks of running, tremendous effort• 100+Gb of scope data, sizable fraction synchronized

with tracking from Bonn telescope• Analysis in progress• Demonstrated good data, now finalizing results, plan to write a paper this year • I believe that we have two viable, complementary

detector concepts• Will need more laser tests, simulation and test beam

before design is finalized• Working on building a U.S. ATLAS collaboration for

Phase 1+2 funding (new effort welcome!)

ATLAS/CMS MCP-PMT Needs• For current QUARTIC design, need about a dozen 10 m pores 64

channel Planacon (or Photek equivalent)• High Rate capability (at 420 m 1% of interactions have a scattered proton).

Start with 13 MHz (75 nsec bunch spacing). Few interactions per crossing, <1 MHz over 12.5 cm2 so should be okay. At max luminosity, 25-30 interactions/crossing at 40 MHz

40 MHz -> 10 MHz over area, may be okay?• 220 m, situation is ~3 times worse!• Need high current capability to improve lifetime of tube: I calculate 10 C over tube in 100,000 hours (1/5 of year) at low luminosity (using 80 pe/event and gain of 106 )• Better grounding• Dropped faceplate?• Other minor improvements?• Phase 1 vs phase 2