9th April 2009 based on a presentation prepared by D. Schinzel

1

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

2

COSMIC RAY DETECTOR

PLAN OF TALK

– 1 Background of idea – 2 Background on muons– 3 General design plan– 4 Things to start doing

9th April 2009 based on a presentation prepared by D. Schinzel

3

• The idea arose because we saw one of these at CERN when we visited last year

• It is a device that demonstrates a bit of physics and engineering, but is also an attractive display to impress visitors (and ourselves)

• It will be hard to build because we don’t even have a complete design (yet), let alone all the smaller details

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

4

• Cosmic ‘Rays’ are actually mostly high energy protons hitting the upper atmosphere

• They produce a ‘shower’ of other sub-atomic particles, but especially fundamental particles called muons

• Muons are a kind of ‘heavy electron’• The really interesting thing about

muons is…

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

5

• The really interesting thing about muons is…

• They are unstable, with a half-life of only about 2 microseconds – which means they can’t reach ground level

• But they can reach ground level!• They live much longer than normal

because for them time is passing very slowly due to their very high speed

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

6

• The detector will be a very large spark detector

• You need some metal plates with a high voltage on them, and a chamber filled with noble gases – helium and argon

• Then, if a muon comes along, it may cause breakdown of the gas, and a spark is formed – with dramatic effect!

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

7

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

8

• The 4 main things to build or obtain are:– The chamber– Source of noble gas with controls– HT supply – 10kV– Electronics to supply the energy for the

sparks, but also to quench them quickly

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

9

• We’ll buy the – Noble gas and pump and fittings– HT supply – 10kV

• We’ll build the – Chamber – hard to do well – low leakage– Electronics – a lot more detail needed

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

10

• Budget:– The absolute outside cost of the project

is £7,000, but I expect to do it for much less

– I don’t yet have a target budget, so that’s a task to be done, but to give you a feel for it, the HT supply may be the single most expensive part, and one could be bought second-hand for about £650

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

11

• Mode of operation:– Two devices called scintillators detect a

muon coming in– Electronics produces a turn-on pulse,

sent to…– A special device called a ‘thyratron’

which enables a spark to occur– The spark’s energy is released from

some high voltage capacitors

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

12

• Trigger Electronics • HV Pulser

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

13

9th April 2009 based on a presentation prepared by D. Schinzel

14

COSMIC RAY DETECTOR

• Top scintillation counter S1

• Trigger electronics

• Bottom scintillation counter S2

9th April 2009 based on a presentation prepared by D. Schinzel

15

• Roles to fill– Project management– Financial management– Mech design and build– Electronic design and build– Gas know-how and procurement– Publicity via website, assemblies etc

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

16

• First tasks – for discussion– Visit Bristol Univ to collect more info and some

scintillators– Visit e2v to see what they can offer us– Produce a draft budget and project plan– Design and build a very small proof-of-principle

chamber and test for gas-tightness*– Design and build the low voltage trigger

electronics and connect to scintillators*– Find out how to buy or make the HT resistors

and capacitors– Find out about thryatrons* please note – the D&T dept are aware of the project but are unlikely to

be able to give much in the way of workshop time due to other commitments

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

17

• No Spark • HV = 2.65 kV

• Trigger given by scintillators S1 and S2

• Thyratron discharges capacitors, then they recharge

• Dead time

COSMIC RAY DETECTOR

9th April 2009 based on a presentation prepared by D. Schinzel

18

• Spark • HV = 4.5 kV

• Trigger

• Spark discharges capacitors

• Dead time

COSMIC RAY DETECTOR