1. Test Beam Studies for FP420 Fast Timing
Developers: UTA (Brandt), Louvain, Alberta, FNAL
WHO?
TB shifters: UTA, UC-London, Louvain, Prague
WHY?
Pileup Background Rejection
Ex: Two protons from one interaction and two b-jets from another
Use time difference between protons to measure z-vertex and compare with tracking z-vertex
measured with silicon detector
How?
How Fast?
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)
Picosecond Workshop
October 16, 2008
IPNL, Lyon

2. Fast Timing Is Hard! ISSUES 3 mm =10 ps Detector Phototube Electronics
Time resolution for the full detector system:
1. Intrinsec detector time resolution
2. Jitter in PMT's
3. Electronics (AMP/CFD/TDC)
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

3. FP420 Baseline Plan 2 QUARTICs 1 GASTOF Lots of 3D silicon
Two 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)

4. 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 within
few ps! 1 measurement of ~10 ps

5. The Detectors : 2) QUARTIC
4x8 array of 6 mm2 fused silica bars
UTA, Alberta, FNAL
Only need 40 ps measurement if you can do it 16 times (2 detectors with 8 bars each)!
proton
photons

6. First TB Results ( Fall 2006)
G1-G2
For QUARTIC bar
110 psec
Efficiency 50-60%
For events with a few bars on see anticipated
√N dependence
<70 psec/Gastof (Burle 25 um 8x8 tube, 4 pixels)
>90% efficiency, dominated by CFD resolution (used Ortec 934)

7. Threshhold discrimination
March 2007 Test Beam
(t)=45 ps
(t)=35 ps
Threshhold discrimination
CFD algo simulated
QUARTIC
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

8. Latest QUARTIC PrototypeHC HH HE
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()

9. QUARTIC 15 mm bar/75 mm guide
20 ps
~ 5 pe’s accepted in 40 ps
20 ps

10. QUARTIC 90 mm bar/0 mm guide
40 ps
40 ps
~ 10 pe’s accepted in 40 ps
40 ps

11. 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

12. Electronics SMA Lemo QUARTIC: Photonis Planacon 10 m pore 8x8 Gastof:
Hamamatsu 6 m
pore single channel
or equivalent Photek
Electronics
Experiment channel
Louvain Custom CFD (LCFD)
Mini-circuits ZX60
6 GHZ or equivalent
HPTDC board
(Alberta)
interfaces to ATLAS Rod
For GASTOF
replace CFD/TDC with single photon
counter
MCP-PMT
Preamplifier
SMA
LCFD
Fast
Scope
Lemo
(b) or (c) TB channel

13. LCFD Luc Bonnet (Louvain) tuned LCFD mini-module to Burle planacon;
12 channel NIM unit

14. June 2008 Test Beam Setup fast timing Cerenkov 3d-sil+Bonn telescope
trigger paddles
comment on
alignment

15. FP420 Timing Setup G2 G1 Q1
Amplifiers

16. Data Acquisition Lecroy 8620A 6 GHz 20 Gs (UTA) Lecroy 7300A
(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

17. Good Trigger is Important
Spray event
add veto

18. channels in adjacent rows
Coherent Noise!
channels in adjacent rows

19. Good Event
5 ns/major division

20. Online Screen Capture one histo is 10 ps per bin others are 20 ps
histogram
delta time
between
channels
FWHM<100
so /2.36
->dt~40 ps

21. 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

22. Determining Pulse Time
Hamamatsu(G1)
Burle (HF)
LCFD (HFc)
Linear fit, use 50% time

23. QUARTIC Long Bars after LCFD
56.6/1.4=40 ps/bar
including CFD! Dt
Time difference between two 9 cm quartz bars after constant fraction discrimination
is 56 ps, implies a single bar resolution of 40 ps

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

25. Tracking /Scope Synchronization
All tracks
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
HEc On
6mm

26. HF Efficiency 6 mm fraction of events with good track and HF bar
on as a function
of track position
6 mm

27. GASTOF Displaced 19 mm See Schul talk All tracks for more details
Multiple scattering
effects in 400 um
wide, 30 cm long stainless steel edge of GASTOF (cause veto)!
1mm depletion implies
tracking projection issues, detector tilted slightly, or both
GASTOF On
dip ~1 mm
wide
edge

28. 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

29. QUARTIC vs GASTOF Do we need both?
G one (or two) measurements 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

30. 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!)

31. 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, 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