R&D Towards a Linear Collider Detector

DOE Site Visit Wednesday July 27, 2011

Senior: Fadeyev, Schumm, Spencer

Students: Bogert, Carman**, Chappelletvolpini*, Cunnington, Gomez, Key, Khan*, Maduzia, Mallory, McFadden, Michlin, Mistry, Moreno, Newmiller, Ramirez, Schier**, Taylor*, Thompson*

* Senior thesis completed** Campus award for senior thesis

Areas of ActivityGeneric Studies

• Charge division• Long-ladder noise

Electronics Development• LSTFE readout• KPIX readout

Radiation Damage• High-dose electromagnetic irradiation

Simulation• Beamline calorimeter reconstruction• Non-prompt track reconstruction

Charge Division

Can a longitudinal coordinate be measured with microstrip sensors?

Explore with PC-board microstrip mock-up and PSpice simulation

Areas of Activity

Long-Ladder Readout Noise

Probe conventional notions about dependence of readout noise on distributed capacitance and series resistance

Standard Form for Readout Noise (Spieler)

Series Resistance

Amplifier Noise (series)Amplifier Noise (parallel)

Parallel Resistance

Fi , Fv are signal shape parameters that can be determined from average scope traces.

Dominant term forlong ladders (grows

as L3/2)

Expected Noise vs. Ladder Length

Series noise expected to dominate for narrow (50 m) pitch sensors above ~25 cm long

“Lumped element” Load

Sensor “Snake”: Read out up to 13 daisy-chained 5cm sensors (with LSTFE-1 ASIC)

Sensor “Snake”

LSTFE1 chip on Readout Board

Can read out from end, or from middle of chain (“center-tap”)

Naïve Prediction vs. Observation

“Lumped” Load

Observed

Exploring Long-Ladder Noise Results

To explore/understand difference between expected and observed, a full network simulation was developed in SPICE by Aaron Taylor ( UNM physics Ph.D. program) and Khilesh Mistry

Comparison with Full Network Model

Full network simulation

Further Reduction: “Center-Tapping”

NIM paper in preparation

Center-Tap Observed

Center-Tap Simulated

The LSTFE Microstrip Readout ASIC

Designed at SCIPP by Spencer, Schumm et al.

Time-Over-Threshold (TOT) Readout: the LSTFE

Pulse-development simulation no loss of accuracy for TOT readout (relative to direct ADC conversion)

Targets low-complexity, long-ladder tracking solution

Real-time readout stream favorable for forward tracking also

LSTFE-I prototype relatively successful; LSTFE II under testing. Upgrades relative to LSTFE-I include

• Improved environmental isolation

• Additional amplification stage to improve S/N, control of shaping time, and channel-to-channel matching

• Improved control of return-to-baseline for < 4 mip signals (time-over-threshold resolution)

• 128 Channels (256 comparators) read out at 3 MHz, multiplexed onto 8 LVDS outputs

FIF

O (L

eadin

g and

trailin

g transition

s)Low Comparator Leading-Edge-Enable Domain

Li

Hi

Hi+4

Hi+1

Hi+2

Hi+3

Hi+5

Hi+6

Li+1

Li+2

Li+3

Li+4

Li+5

Li+6

Proposed LSTFE Back-End Architecture

Clock Period = 400 nsec

EventTime

8:1 Multi-

plexing (clock = 50 ns)

Some early results: TOT respone

Tim

e ov

er T

hre

shol

d (

s)

Tim

e ov

er T

hre

shol

d (

s)

Minimum ionizing region

Very uniform response for large pulses; increased sensitivity in min-i region

More early results: Noise v. Capacitive Load

Result at 100 pF (optimization point): 1375 electrons noise, but without detector resistance (distributed RC network)

Use of the SLAC KPiX Chip for Tracking

SCIPP charged with looking at KPiX in the one-few fC range (tracking regime)

0-Charge Input Offset (mV) by Channel(x

10)

Offset in mV for no

input charge

Four mis-behaving channels

KPiX 7

Window of operating thresholdsVery narrow!Need to consider for further KPiX versions…

Number of channels with occupancy greater than 0.1%

Number of channels with efficiency less than 99.9%

KPiX 7

Use SCIPP pulse-development simulation to

assess impact of offset variation

The ILC BeamCal:

Radiation Damage Studies

Reconstruction Studies

25

The Issue: ILC BeamCal Radiation ExposureILC BeamCal:

Covers between 5 and 40 miliradians

Radiation doses up to 100 MRad per year

Radiation initiated by electromagnetic particles (most extant studies for hadron –induced)

EM particles do little damage; might damage be come from small hadronic component of shower?

26

Irradiation PlanUse existing Micron sensors from ATLAS R&D• n-type and p-type• Standard float-zone and Magentic Czochralski• Runs of 0.1, 0.3, and 1 GRad for each sample• Runs with samples far from radiator (no hadronic effects)Total integrated dose of ~10 Grad

Will assess the bulk damage effects and charge collection efficiency degradation.

Sensors

Sensor +FE ASIC

DAQ FPGA with Ethernet

Charge-Collection Modularization Activity

• Can connect multiplicity of Sensor Board modules to PMFE w/out wire-bonding

• Requires development of 6 PCB/litho components (Donish Khan; accepted to Stanford Ph.D. program)

BCAL Simulation

Alex Bogert:

• Geometry and virtual segmentation• Overlay• Mean pair background subtraction• Developing high-energy electron pattern recognition

Average Deposited Energy per Layer

Background

Signal

Pair Background Energy Fluctuations

Non-Prompt Tracking with the SiD

Explore performance via explicit signature: Metastable stau NLSP (Gauge-Mediated SUSY)

Reconstructing Metastable Staus w/ SiDGauge-Mediated SUSY

• Large tract of parameters space as stau NLSP

• Metastable (cstau ~ centimeters) is in cosmologically preferred region

Process is

with

~~ee

~

G~

cmc 23

Reconstructing Metastable Staus w/ SiD

Started with:

5+1 layers for inside track

4 layers for outside track

New result: Include VTX-only inside track

Measuring Staus with the SID

Stau sample:

11.1 fb-1 of e+e- stau pairs with

• mstau = 75 GeV

• Ecm = 500; = 90 fb

• c = 23 cm

Background sample:

5.3 fb-1 combined SM background

Reconstructing Metastable Staus w/ SiDFocus initially on rdecay = 22-47 cm…

Reconstruct decays by requiring:

    - Outer hit of inner trk on last VXD or 1st tracker layer    - 1 missing layer between inner & non-prompt trks    - Both tracks on the same side of the Barrel (in z)    - Tracks have a geometric intersection in the x-y planeAnd: When inside track has 1 Central Tracker Hit    - The sign of the track curvatures match

    - Non-prompt track curvature larger than the primary

Of 897 staus with 6cm < rdec < 47cm, 642 staus are reconstructed, of which 592 truth-match

Stau Reconstruction Efficiency

Truth-Matched Staus

Signal to Background for 10 fb-1

Signal to Background (10 fb-1)

Good separation between signal and background for #prompt tracks/event and inside track pt

Require, e.g., fewer than three prompt tracks

#Prompt Tracks/eventpT of inside track

Reconstructing Metastable Staus w/ SiDStarted with:

5+1 layers for inside track; 4 layers for outside track

New result: Include VTX-only inside track

Next step: Try to use cal-assisted tracking to get three-hit kinks (dedicated recon-struction by Mallory, Michlin, Bogert)

Wrap - Up

Many projects underway:

• Charge-division study published• Ladder noise study in preparation for publication• Electronics development proceeding• Simulation studies bearing fruit• New BeamCal contribution in full swing• Meaningful research experience for many undergraduates; 8 theses in past three years, including two campus-wide thesis awards

Backup Slides

Areas of Activity