Transcript LED beacons in KM3NeT

LED beacons in KM3NeT
pulse drivers
Jonathan Perkin - University of
Sheffield
Sub nanosecond time
resolution (xyz < 0.1m)
• Can be achieved through
– Clock + Acoustic Positioning + OM LED
– Clock + Acoustic Positioning + Beacon
– Clock + Acoustic Positioning + Atm.Nu
• Beacons (LED / LASER / both) not
necessarily required for sub nanosecond
timing, so why use them?…
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
2
Motivation for LED
beacons…
• Beacons put light into the detection medium
– enable us to test propagation of a known signal
• Redundancy in the calibration system is a good
thing
– reduces systematics
• Atmospherics not a clean signal
– due to event multiplicities
• LED beacon electronics in principle could use same
housing as the other detector elements
– easy to manufacture
• LED beacons are robust and can be incorporated
into any kind of fibre / copper architecture
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
3
Improvements to ANTARES
pulsing circuit
• Attempts have been made to further reduce
rise time and FWHM of pulse through
redevelopment of the drive circuit
• A new circuit design has been proposed [PhD
thesis, Omar Veledar, [email protected]]
• Again it is based on the complimentary
(transistor) pair regenerative switch as
proposed by Kapustinsky et al (1985)
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
4
Basic drive component
• The complimentary pair regenerative
switch configuration
1. First, charge C1 through R1
R3 > R2 so voltage divider R2/R3
means Vref is small
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
5
Basic drive component
• The complimentary pair regenerative
switch configuration
1. First, charge C1 through R1
2. When VC1>Vref+VQ1BE Q1=on
Emitter
Base
Collector
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
6
Basic drive component
• The complimentary pair regenerative
switch configuration
1. First, charge C1 through R1
2. When VC1>Vref+VQ1BE Q1=on
3. Current thru Q2B  Q2=on
Emitter
Base
Collector
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
7
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
Saturday, April 25,
2020
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
Jonathan Perkin - University
of Sheffield
8
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
5. Consequence of this is Vref drops
voltage divider R2/R4 < R2/R3
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
9
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
5. Consequence of this is Vref drops
6. Because Vref falls down, Q1
switches on harder
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
10
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
5. Consequence of this is Vref drops
6. Because Vref falls down, Q1
switches on harder
7.  more base into Q2
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
11
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
5.
6.
7.
8.
Saturday, April 25,
2020
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
Consequence of this is Vref drops
Because Vref falls down, Q1
switches on harder
 more base into Q2
Q2 switches on harder, with Q1
and Q2 on, C1 discharges quickly
Jonathan Perkin - University
of Sheffield
12
Basic drive component
• The complimentary pair regenerative
switch configuration
1.
2.
3.
4.
Saturday, April 25,
2020
First, charge C1 through R1
When VC1>Vref+VQ1BE Q1=on
Current thru Q2B  Q2=on
With Q2 on, current thru R2 prefers
route thru R4
5. Consequence of this is Vref drops
6. Because Vref falls down, Q1
switches on harder
7.  more base into Q2
8. Q2 switches on harder, with Q1
and Q2 on, C1 discharges quickly
9. Circuit regenerates when
VC1< Vref+VQ1BE Q1 and Q2 switch
off
Jonathan Perkin - University
13
of Sheffield
Pulse shaping
• In addition to regenerative switch, both drivers have
pulse shaping components
• New driver features a shorted turn transformer,
replacing original inductor
• Again this reverse biases the pulse, shortening the
FWHM
• a back EMF is induced in shorted turn to enhance the
reverse biasing
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
14
Results from new pulsing
Rise(ns) Fall(ns) FWHM(ns)
circuit
ANTARES
2.47
4.33
4.24
NEW
1.98
3.72
3.86
%improvement
20%
14%
9%
(Average of 1000 measurements from 8x HLMP-CB15,
470nm LEDs using 1” Hamamatsu PMT)
A ~10-20% improvement in pulse shape is observed using
new driver
Incorporating this with brighter LEDs e.g. NSPB500S
(~10x brighter)  scope for use in km3 detector?
Saturday, April 25,
2020
Jonathan Perkin - University
of Sheffield
15