Autonomous rate measuring system
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Autonomous Rate Measuring System. Theodoros Athanasopoulos Representing the KM3NeT Consortium Nestor Institute For Astroparticle Physics VLV v T09 Athens 13 th – 15 th October 2009. Autonomous Rate Measuring System. Target of the experiment

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Autonomous rate measuring system

Autonomous Rate Measuring System

Theodoros Athanasopoulos

Representing the KM3NeT Consortium

Nestor Institute For Astroparticle Physics

VLVvT09

Athens 13th – 15th October 2009

VLVvT09 Theodoros Athanasopoulos


Autonomous rate measuring system1

Autonomous Rate Measuring System

  • Target of the experiment

    To measure the effect of sedimentation and bio-fouling on the glass surface of optical modules deployed in the deep sea.

  • How do we measure?

    We will periodically measure and record the singles at ½ spe and doubles (in a 10ns window) PMT rates caused mainly by K40 decays and monitor the gain by recoding the single photoelectron pulse height.

VLVnT09 Theodoros Athanasopoulos


Autonomous rate measuring system2

Autonomous Rate Measuring System

An Autonomous System

The PMT Rate Measuring System is an autonomous system, battery powered, designed to operate for more than 1 year with data recorded in memory and monthly transfers acoustically to surface. Due to limited battery life of the acoustic modem, data transmitted has been designed to be only 40kB per month.

Battery life is also an issue for the rest of the electronics so low power electronics have been designed and developed for this system.

The system will be in sleep mode most of the time. It will turn on only for 1 hour every week to take the measurement, store the data and go to sleep mode again. It will also wake up to transmit the data upon acoustical request.

System total power consumption is:

On Mode: 40W=> 40W x 52h = 2080Wh Total power consumption = 3219Wh

Off Mode: 130mW => 130 x 8760h = 1139Wh Total power supplied = 8400Wh Use of alkaline batteries

VLVnT09 Theodoros Athanasopoulos


System description mechanical

System Description (Mechanical)

APPARATUS LAYOUT (Side View)

8 Optical Modules (4 pairs)

Battery bank x 4

VLVnT09 Theodoros Athanasopoulos


System description electronics

Acoustic Modem

OM1

Board to FPGA buses

SD

1GB

4 Channel Discriminator MAX964

OM2

4 Channel ADC AD7476

System Description (Electronics)

FPGA

Spartan 3E

OM3

14bit bus

μController

PIC18F4550

OM4

4 Channel Discriminator MAX964

OM5

4 Channel ADC AD7476

8ch HV Control

Slow Controls

OM6

8ch HV Monitor

Power Regulation &

Power Distribution System

OM7

OM8

VLVnT09 Theodoros Athanasopoulos


Assembled system

Assembled System

FPGA Board

Power Regulation and Power Distribution Unit

VLVnT09 Theodoros Athanasopoulos


Front end electronics

Front End Electronics

From Other

Discriminators

Coincidence Logic

Inverted and

amplified PMT

Pulse

To Doubles Rate

Counter

Discriminator

Pulse

Discriminator

½ SPE

AMP

To Singles Rate

Counter

PMT Pulse

Peak and Hold

ADC

VLVnT09 Theodoros Athanasopoulos


Conclusion

Conclusion

We have designed a low power autonomous system to measure the K40 rate to stay in the sea for more than one year. It will be sensitive to reductions in the singles and doubles rate at single photoelectron conditions due to sediment adhesion.

Data will be retrieved periodically acoustically.

Expected deployment end of this month. System is currently being tested at the Nestor Lab.

VLVnT09 Theodoros Athanasopoulos


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