Transcript Event Mode Data Acquisition System Richard Riedel, Oak Ridge National Laboratory

Event Mode Data
Acquisition System
Richard Riedel, Oak Ridge National Laboratory
Event Mode In a Nutshell
 Every neutron detected is time stamped and saved without
histogramming.
 Other variables are also time stamped producing a movie
like data set at run end.
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Why Event Mode?
 This what detectors do (where and when a neutron is
detected)
 “Electronic time-focusing of pulsed-source neutron chopper
data: binning to minimize effects of proton pulse and
chopper opening time variations” JM Carpenter NIM vol 429
2001
 Pulse Probe Techniques
 Cross-Correlation Techniques.
(Corelli, which measures single crystal diffuse scattering
using cross correlation to provide elastic discrimination)
 Offers novel approaches to typical data acquisition
problems
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Histogram
Original Space nor Time resolution necessarily preserved…
histogramming is a destroyer of information
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Also Need Hardware Gating
Histogram neutrons only when
temperature is within some
range of setpoint
gate control
from preamp or shaper
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Event Based System Requirements
 No hardware histogramming.
 Ability to timestamp detected neutrons.
 Log with time/date stamp ancillary variables (i.e. temp,
magnetic fields etc.).
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Event Mode Paradigms
 Gating is done at the reduction/analysis level not in the DAS
hardware.
 Histogramming is done at the reduction/analysis and can be
modified as needed without affecting the underlying data.
scattering data
software with sort criteria
data from file stream
or live stream
gated data
temperature logs
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
 Variables
can be calculated without histogramming first.
d  /sin
Event
Pixel ID
tof
sine lookup
Software: a few
multiplies, additions
and if statements
Increment this bin
Could put a software gate here.
Its easier to throw data out then to look at data that was never collected.
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Event Mode Data Format
Time Stamp [31:0]
Uncorrected time of flight
Position Index [31:0]
Pixel ID of detected neutron
Array of event structure
Standard neutron event data generated by all detector electronics at the SNS
+
Pulse ID [63:0]
Pulse ID from accelerator
Zero Based Starting Index [63:0]
Index of starting neutron event structure
that was produced with the above pulse ID
Array of pulse info structure
Standard pointer array which associates a pulse ID with a set of event data.
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
SNS Implementation
C++ Abstraction Classes
Detectors
Common Data Format
Common C++
Code
Class
xxx
Independent of Detector
System
UDP
Broadcast
(Command
Handling
Data transfer
functions.)
Class
yyy
Class
zzz
Detector Electronics
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Broadcasting the Data Stream
Guaranteed Delivery To One Point
Preprocessor
Passive Client
Passive Client
Active Client (DFS)
Session Header
Header ACK
Data Packet #0
Packet #0 ACK
Data Packet #n-1
Packet #n-1 ACK
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Transmission Benchmarks
Round Trip Time vs. Paylaod (SNS UDP protocol)
Send Time + Ack Time (usec)
3000
2500
2000
with switch
witout switch
1500
1000
500
0
0
10000
20000
30000
40000
Payload Bytes.
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Sample Live Views From Control Computer
Mag. Refl. 2D He3 Gas Detector
SNAP .5M pixel Anger Camera
Both instruments see same event format!
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Additional Listeners Can Do Real Time
Independent Work
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Most Interesting Applications Require
Additional Time Stamped Data
Position,TOF
+
Chopper Phase
=
Pulse Information
Temperature, Stress…
Preprocessor,
Receives Events
from
Electronics and adds
TOF correction.
Data
File Server
SNS DAS streams,
event data……
Event Data
Data Streamed to both
Control Computer and
Data File Server (16.7 100 msec time frame)
Control
Cross, AutoCorrelations,
Computer
Dynamics, Phase Transitions,
Kinetics and
Both c.c. and dfs
Transient Phenomenon
bin event data as
directed
Detector Electronics
P.P Master
Maintains listing of chopper
phases
Per pulse
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Detectors
Adding Chopper Phases/Other Variables
 Requires DAS Hardware Sync signal.
High Frequency Signals
 Require Access To Accelerator Time Stamp Broadcast.
 Requires Computer Clock to be synced with accelerator
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Low Frequency Signals
Stress Strain Example
Stress Waveform
Proton Pulses
Strain Transducers
time
Strain Sample Times
Data Set
Sync. Pulse
1000
PulseID
33
Stress Strain Preprocessor
1010
124567980
35
0
1020
124568869
31
PulseID Broadcast
Data Set=two binary files
VULCAN will have the capability to do
cross correlation technique
1025
33
1000
34
1008
34
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
4
How Time Synchronization Is Done
Satellite Computers:
Chopper, Sample Environment etc.
Tier 2
Tier 1
Preprocessor
NTP
Tier 0
NTP sets local
time, UDP
broadcast
sends
accelerator
time stamp
ETC
Accelerator Time
Stamp (60Hz)
Timing
PC
NTP only
Control Computer
Interrupt Based
Driver/Service
(50usec
latency)
NTP to sync computer time,date clock
UDP broadcast for computers that must
associate additional
data with accelerator time stamp (pulseid).
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Final File Set
Pairs of binary files
Neutron
data
pulseid
Chopper
Phases
pulseid
X
Variable
pulseid
+
not the same!
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
SQL Like Queries are Possible
 SELECT pulses FROM run3100 WHERE temperature > 10
AND temperature < 20;
 SELECT tof FROM run3100 WHERE pixelid=1101 OR
pixelid=1102;
 Would require a abstraction of file system. (Embryonic SQL
queries available now for current values).
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Who Else Runs An Event DAQ?
Particle Physics.
ATLAS DAQ system
Reduction,
Data Sorting,
Analysis
Event Data
NOMAD rates…up to 500MB/s
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY