APEX Software
Seamus RiordanStony Brook University
April 19, 2015
Seamus Riordan — APEX 2015 APEX Soft 1/25
Outline
HRS VDCs and APEX
High Rate Tracking Performance
Optics Going Forward
Seamus Riordan — APEX 2015 APEX Soft 2/25
Basic VDC Operation
Tracks enter nominally 45◦, produce signals on 3-7 wires
Drift time patterns among several wires matched to construct“cluster”
2 U-plane and 2 V-plane clusters fit to recreate full 3D track
Ci+4
Ci+3
Ci+2
Ci
Ci+1
di+2
crossover
point
id
di+3 di+4
D=13mm
wire plane
4.24mm
"pivot wire"
τslope
di+1
(HV) plane
cathode
(HV) plane
cathode
particle trajectory
Drift Time (ns)50 0 50 100 150 200 250 300 3500
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
Drift Time Spectrum, U1
Seamus Riordan — APEX 2015 APEX Soft 3/25
VDC Modifications
Modifications for performance up to 5 MHz (full experimentluminosity).
Standard APEX High RateHV −4.0 kV −3.5 kVDisc. LeCroy (Ith = 8 µA) JLab Custom (Ith = 1 µA)Gas 60-40 Ar/CH2 60-40 Ar/CH2
Max Rate 500 kHz 5 MHzGain 20× 103 25× 103
Max VDC current draw I/wire/cm ∼ 5 nA
For APEX, QVDC < 0.1 C (no serious aging)
Seamus Riordan — APEX 2015 APEX Soft 4/25
Tracking Algorithm - Clustering
Ci+4
Ci+3
Ci+2
Ci
Ci+1
di+2
crossover
point
id
di+3 di+4
D=13mm
wire plane
4.24mm
"pivot wire"
τslope
di+1
(HV) plane
cathode
(HV) plane
cathode
particle trajectory
→
Wire Number160 162 164 166 168 170
Dri
ft T
ime (
ns)
50
0
50
100
150
200
VDC U1
Algorithm scans for ’V’ shaped clusters in time
Hits in each cluster must be within reasonable time constraints
Allow for gaps of 1 wire, must have 3 ≤ wires in cluster ≤ 7
Time of the cluster is offset, calculated through fit based ontime-to-drift distance mapping
Time resolution from fit on σt ≈ 15 ns
Seamus Riordan — APEX 2015 APEX Soft 5/25
Advanced Scanning
Wire Number0 50 100 150 200 250 300 350
Dri
ft T
ime (
ns)
100
0
100
200
300
400
500
VDC U1
Multihit TDC information used since rates are high
Earliest hits used to fit clusters
Several passes over data taken to maximize clusters foundwhen separated in time, but not space
Seamus Riordan — APEX 2015 APEX Soft 6/25
Tracking Algorithm - UV Association
Cut on U cluster, V cluster time difference w/ trigger, ±40 ns
Cluster positions must be in chamber active area
Time Difference (ns)100 80 60 40 20 0 20 40 60 80 1000
500
1000
1500
2000
2500
VDC UV Cluster Time Difference
Select clusters
near in time
VDC UV Cluster Time Difference
Ambiguity prevents uniqueassociation between U-V clusters
If ambiguity in UV association, no tracks are returned
Seamus Riordan — APEX 2015 APEX Soft 7/25
Tracking Algorithm - Track Fitting
All chamber 1 - chamber 2 UV clustersbuilt
Sort by χ2 based on angularinformation from drift time fit
Accept as many χ2 clusters untilmaximum found
Seamus Riordan — APEX 2015 APEX Soft 8/25
Tracking Efficiency
Tracking efficiency found in left arm for:
Left arm s2m scintillator triggerHigh preshower+shower calorimeter signal (e−)
Low rate, 0.3 MHz
Cluster Size
2 3 4 5 6 7 80
2000
4000
6000
8000
10000
12000
14000
16000
18000
u1 Cluster size 2uA Tantalum
Highest rate, 5 MHz
Cluster Size2 3 4 5 6 7 8
0
2000
4000
6000
8000
10000
u1 Cluster size High Current Lead
Average wires in clusters become smaller at high rate due toefficiency
Seamus Riordan — APEX 2015 APEX Soft 9/25
Tracking Efficiency
Can take low rate as base and calculate how it shifts for hitinefficiencies
2 3 4 5 6 7 80
5000
10000
15000
20000
2 3 4 5 6 7 80
2000
4000
6000
8000
10000
12000
14000
16000
Have ∼ 92% hit efficiency
Expect 2% loss of tracking efficiency with hits < 3
Seamus Riordan — APEX 2015 APEX Soft 10/25
Tracking Efficiency
Can take low rate as base and calculate how it shifts for hitinefficiencies
Cluster Size2 3 4 5 6 7 8
0
2000
4000
6000
8000
10000
u1 Cluster size High Current Lead
2 3 4 5 6 7 80
2000
4000
6000
8000
10000
12000
14000
16000
Have ∼ 92% hit efficiency
Expect 2% loss of tracking efficiency with hits < 3
Seamus Riordan — APEX 2015 APEX Soft 10/25
Tracking Efficiency - II
From Eric’s thesis:
Required coincident event and then frequency of how often atrack was found in an arm99.0% for LHRS, 98.2% for RHRSClose enough with simple cluster argument?
Seamus Riordan — APEX 2015 APEX Soft 11/25
Tracking Efficiency - Losses
Losses come from:UV association ambiguityNo clusters found (bad timing structure, overlapping, hitinefficiency)
LHRS, Single Arm Trigger:
Trigger Rate (MHz)0 1 2 3 4 5 6
Fra
cti
on
al L
oss
0
0.1
0.2
0.3
0.4
0.5 Total Loss
Loss from Ambig.
Loss from No Clusters
Event Loss
Loss goes up to 40% for highest current running
Seamus Riordan — APEX 2015 APEX Soft 12/25
Efficiency Improvements
Tracking Work To Do:
UV ambiguity may be broken through use of other detectors,χ2 fitting, geometry considerations, event distributionconsiderations
Some clusters from “no cluster” events may be recoveredthrough better cluster searching code
Try to understand how spurious clusters are generated - G4simulation?
Seamus Riordan — APEX 2015 APEX Soft 13/25
Overview and Strategy
APEX has unique optics requirements
FOM is driven by scattering angle resolution rather thanmomentum resolutionSeptum needed to go from 6◦ to 12.5◦
Requires careful examination of HRS tune to optimize
John LeRose is gone so we have to think through much of thisourselves
Have produced 2nd order transport matrices for ideal case asstarting test ground
Confirmation in existing ray tracing required for final result
Seamus Riordan — APEX 2015 APEX Soft 14/25
Optics Overview
1.80
1.80
4.42
3.57
1.50
1.25
0.80
1.69
45°30°
30°
8.40
10.37
3.05
HRS Design Layout(design magnet effective lengths displayed)
Q1Q2
Dipole
Q3
20.76
1st VDC Plane
Dimensions in meters
1 m
θ0
φtg y
tg
ysieve
z
Sieve plane
Beam
Scattered
electron
L
D
Hall centerzreact
ytg
tg
central ray
Spectrometer
Using idealized representation of HRS first and secondorder elements can be calculated
Excellent primer for framework
http://cds.cern.ch/record/283218/files/SLAC-75.pdf
http://github.com/seamusriordan/hrstrans
Seamus Riordan — APEX 2015 APEX Soft 15/25
APEX Tune - Simple Optimization Attempt
t [m]0 5 10 15 20 25
4−
2−
0
2
4
6
8
10
12
14
)tg
(x|x)tgθ(x|
)δ(x|
x Couplings
t [m]0 5 10 15 20 25
2−
0
2
4
6
8 )tg
(y|y)
tgφ(y|
y Couplings
Using first order code allows for rapidcalculation of acceptance and matrixelements
A fitter is used which
Preserve acceptance for targetlength (as seen at 6◦)Produce first order reconstructionmatrix by inverting transportMinimize reconstruction elementsof φtg with VDC spatial/angularresolutions
Immediately drove (y |ytg) coupling tozero and increased (y |φ)
About the same acceptance - butserious losses in momentum and vertexresolution (> factors 2?)
Seamus Riordan — APEX 2015 APEX Soft 16/25
APEX Tune - Simple Optimization Attempt
θ0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedθ
y [m]0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Y Origin - Accepted
φ0.1− 0.05− 0 0.05 0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Origin - Acceptedφ
δ0.1− 0.05− 0 0.05 0.1
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedδ
Using first order code allows for rapidcalculation of acceptance and matrixelements
A fitter is used which
Preserve acceptance for targetlength (as seen at 6◦)Produce first order reconstructionmatrix by inverting transportMinimize reconstruction elementsof φtg with VDC spatial/angularresolutions
Immediately drove (y |ytg) coupling tozero and increased (y |φ)
About the same acceptance - butserious losses in momentum and vertexresolution (> factors 2?)
Seamus Riordan — APEX 2015 APEX Soft 16/25
Summary and Work To Do
Tracking generation for trying to match all clusters is about60% at 5 MHz trigger, can this be understood?
John LeRose’s files were recovered and are available - I haveaccess to SNAKE and the files used for standard tune, PREX,and have been using them
Need to include our new septum, produce full polynomialtransport, verify acceptance and reconstruction
I believe this is a project which we can handle on our own andthis is at a point where a grad students could get involved
Seamus Riordan — APEX 2015 APEX Soft 17/25
BACKUP SLIDES
Seamus Riordan — APEX 2015 APEX Soft 18/25
HRS Vertical Drift Chambers
45O
Side view
Top view
nominal particle trajectory
Upper VDC
Lower VDC
2118 mm
288 mm
nominal particle trajectory
d =335mmv
d =335mmu
v2
d =26mmuv1
d =26mmuv2
v1
u1
u2
U1
V1
U2
V2
Nominal Characteristics
U/V angle ±45◦
Sense wires/plane 368Wire Spacing 4.24 mm
Pos. Res ∼ 100 µmAng. Res ∼ 0.5 mrad
Seamus Riordan — APEX 2015 APEX Soft 19/25
Pre-test run PAC Requirements
Requested for test run by PAC:Prove that the vertical drift chambers (VDCs) can operate ata rate higher that 20 kHz/wire (that, according to the TACreport, is the maximum Hall A has operated till now).
VDCs had not been run at such high rate (for extended periodof time)
Required to go to ∼ 5 MHz (75 kHz/wire)
Requires hardware modifications to run efficiently withoutsevere aging
Seamus Riordan — APEX 2015 APEX Soft 20/25
Timing Offset Calibration
VDC requires software offsets for drift time
Calibrated in groups of 16 wires (discriminator inputs)
500 600 700 800 900 1000 1100 1200 1300 14000
20
40
60
80
100
120
140
u1 TDC grp 8u1 TDC grp 8
Calibration done by fitting time dist. peak and fixed at 1.4 σearlier from peak (arbitrary)
Seamus Riordan — APEX 2015 APEX Soft 21/25
Timing Offset Calibration Results
Calibration is done to ∼ ns level
Offsets may be different for different triggers
Minimized in hardware to ∼ 10 ns level, fully corrected insoftware
wire group number0 2 4 6 8 10 12 14 16 18 20 22 24
Mean
Peak P
osit
ion
(n
s)
15
16
17
18
19
20
21
22
23
24
25
time (ns)-50 0 50 100 150 200
No
rma
lize
d e
ntr
ies
0
50
100
150
200
250
300
350
400Trigger1
Trigger2
Trigger3
Trigger4
Trigger5
Trigger6
Seamus Riordan — APEX 2015 APEX Soft 22/25
Drift Time-to-Distance
Drift time-to-distance conversion follows form:
Theta dependence:
v2t < 0 : d = v2t
0 < v2t < a1 : d = v1t = v2t
(1 +
a2
a1
)a1 < v2t : d = v2t + a2
a1 and a2 carry tan θ = ∆z∆r dependence (r = u or v)
a1 =3∑
i=0
a1,i tani θ
a2 =3∑
i=0
a2,i tani θ
Seamus Riordan — APEX 2015 APEX Soft 23/25
TTD Calibration
No serious differences between high and low rate data
Restricting to slice in incident angle θ:
Low Rate, 0.4 MHz
Drift Time (ns)50 0 50 100 150 200 250 300
Dri
ft D
ista
nce (
m)
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
TTD Function
|<5 mradfp
θTTD, low current, |
High Rate, 4.6 MHz
Drift Time (ns)50 0 50 100 150 200 250 300
Dri
ft D
ista
nce (
m)
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
TTD Function
|<5 mradfp
θTTD, high current, |
Small recalibrations for θ dependence are necessary
Seamus Riordan — APEX 2015 APEX Soft 24/25
TTD Calibration
Requires some θ dependence re-fitting
Discrepancies are in the tail on the level of 20 µm
(rad)fp
θ
0.1 0.05 0 0.05 0.1
Resid
ual (m
)
0.002
0.0015
0.001
0.0005
0
0.0005
0.001
0.0015
0.002
fpθU1 Residual vs.
Seamus Riordan — APEX 2015 APEX Soft 25/25
Tracking Resolutions
Track resolutions found through residuals of full χ2 fit
Residual (m)0.003 0.002 0.001 0 0.001 0.002 0.003
0
2000
4000
6000
8000
10000
12000
14000
mµRes. = 354.0
U1 Residual
Second, broader Gaussian distribution appears at high rate
Should be fitting to students t distribution with mult scatt
Corresponds to 100 µm, 0.3 mrad detector resolution
Seamus Riordan — APEX 2015 APEX Soft 26/25
Tracking Efficiency
Tracking efficiency found in left arm for:
Left arm s2m scintillator triggerHigh preshower+shower calorimeter signal (e−)
Low rate, 0.3 MHz
N Clusters0 2 4 6 8 10
0
2000
4000
6000
8000
10000
12000
+/ 40ns
No ambiguity
Used in track
u1 Clusters in 40 ns 2uA Tantalum
Highest rate, 5 MHz
N Clusters0 2 4 6 8 10
0
2000
4000
6000
8000
10000
12000+/ 40ns
No ambiguity
Used in track
u1 Clusters in 40 ns Highest Current Lead
Average wires in clusters become smaller at high rate due toefficiency
Seamus Riordan — APEX 2015 APEX Soft 27/25
Event distribution
Event distribution has small distortions due to non-uniformefficiency
How does this affect the acceptance?
Xdet
(m)det
x1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
0
50
100
150
200
250
300
350
310×
0.4 MHz, Lead
4.6 MHz Lead
Detector X Distribution, S2m trigger (T1), Normalized to charge and prescales
Ydet
(m)det
y0.06 0.04 0.02 0 0.02 0.04 0.06
0
100
200
300
400
500
600
700
800
900
310×
0.4 MHz, Lead
4.6 MHz Lead
Detector Y Distribution, S2m trigger (T1), Normalized to charge and prescales
Seamus Riordan — APEX 2015 APEX Soft 28/25
Standard Tune Comparison
x-plane
z0 5 10 15 20
-6
-4
-2
0
2
4
6
8
10
12
<x|θtg>
y-plane
z
0 5 10 15 20
-4
-2
0
2
4
6
8
Q1 Q2 Q3Dipole
Q1 Q2 Dipole Q3
<x|xtg>
<x|δ>
<y|φtg>
<y|ytg>
[m]
[m]
[m]
[m]
t [m]0 5 10 15 20
4−
2−
0
2
4
6
8
10
12
)tg
(x|x)tgθ(x|
)δ(x|
x Couplings
t [m]0 5 10 15 20
2−
1−
0
1
2
3
4
5
6
7)
tg(y|y
)tg
φ(y|
y Couplings
Framework does a reasonably good job of recreating firstorder elements
Acceptance ∼ 6 msr using simple aperture cuts
Seamus Riordan — APEX 2015 APEX Soft 29/25
APEX Tune
APEX test run ran with special tune which nominally reproducesstandard tune optics and acceptance but with pure (y |φ) coupling
Standard Optics
t [m]0 5 10 15 20
4−
2−
0
2
4
6
8
10
12
)tg
(x|x)tgθ(x|
)δ(x|
x Couplings
t [m]0 5 10 15 20
2−
1−
0
1
2
3
4
5
6
7)
tg(y|y
)tg
φ(y|
y Couplings
→
APEX Test Run Configuration
t [m]0 5 10 15 20 25
4−
2−
0
2
4
6
8
10
12
14
)tg
(x|x)tgθ(x|
)δ(x|
x Couplings
t [m]0 5 10 15 20 25
2−
0
2
4
6
8
)tg
(y|y)
tgφ(y|
y Couplings
Seamus Riordan — APEX 2015 APEX Soft 30/25
APEX Tune
APEX test run ran with special tune which nominally reproducesstandard tune optics and acceptance but with pure (y |φ) coupling
Standard Optics
θ0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedθ
y [m]0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Y Origin - Accepted
φ0.1− 0.05− 0 0.05 0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Origin - Acceptedφ
δ0.1− 0.05− 0 0.05 0.1
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedδ
→
APEX Test Run Configuration
θ0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedθ
y [m]0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2
0
0.05
0.1
0.15
0.2
0.25
0.3
Y Origin - Accepted
φ0.1− 0.05− 0 0.05 0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Origin - Acceptedφ
δ0.1− 0.05− 0 0.05 0.1
0
0.05
0.1
0.15
0.2
0.25
0.3
Origin - Acceptedδ
Seamus Riordan — APEX 2015 APEX Soft 30/25