# Lasersystem

##The laser tube itself##

The tube is 1600 mm long. Ground connector and water outlet is at the output end.

##HV PSU##

Pinout:

1. Enable - Active low - Internal Pull down
2. Enable - Active low - Internal pull up
3. Enable - Active low - Internal pull up (possibly slow, meant for interlock)
4. GND
5. Modulation (0 V = min, +5 V = max)
6. +5 V out

All the enable inputs have to be active (low) for the laser to fire.

If left unconnected input 1 will be active, 2 and 3 will be inactive.

##Cooling##

The laser tube will need water cooling, so for testing and later use I've added some nice silicone tubing and some fittings that allow us to use the pumps and radiators donated by Rune.

###Chiller###

Keeping the water temperature down to 30 deg is going to be very hard using only radiators and fans, so we might need to build a phase-change chiller, which uses a compressor to keep the reservoir temperature down to 20 deg C.

Dennis Nielsen is building a chiller, we still need to add a buffer tank and an extra pump with active control that can circulate water through the chillers heat exchanger.

###Cooling calculation###

• Specific heat of water (C): 4.185 J/(g*T)

Power can easily be calculated as a function of water flow and temperature difference: P = mTC

Let's say we measure 3 degrees of temperature drop over the radiator, at the minimum 4 liter / minute P = (4000/60) g/s * -3 K * 4.185 J/(g*T) = -837 Watt

###Measurements on actual cooling system###

Measuring the input and output temperature along with the flow rate shows that the tube outputs around 275-300 Watt of heat when running at full power, which means that it has an efficiency of around 20% or that we get much less than 80W out of it.

##Progress##

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