Step 1: Material
1x 1 meter of 12mm copper pipe
2x 12mm copper end caps
1x Cree XLamp XR-E-B3 465nm-470nm Blue LED (XREBLU-L1-0000-00K01) presoldered onto a 20mm PCB board
(Note: the 16mm PCB board might fit better on the end cap but will be more difficult to solder onto the endcap because of its smaller size)
1x 1 Ohm resistor rated above 1W
1x Suitable power supply (DC 3.3-3.7V@1A)
Warning: If you use a USB 3.0 port. Make sure the port can handle more than 1A. Some Gigabyte motherboards have 3x-USB-power. On its USB-3 ports this means 3 x 900mA = 2700mA.
Step 2: Clean and Tin One End Cap
Do the same with the backside of the Cree PCB board. Some scratching and carving of the PCB board with a small screwdriver might also improve the tensile strength of the solder joint.
Step 3: Attach the Cree P4 to the Pipe
With the stick upright create a pool of soldering tin on the top of the end cap. I used an oven lighter in unison with a 50W soldering iron. The end cap and the stick will get very hot.
Place the Cree P4 in the pool of soldering tin on top of the end cap. Center the PCB board. The PCB will cool down and harden the solder quickly.
File down the Cree along the edges of the end cap if necessary.
Step 4: Solder Wires to the Cree P4
Use some heat shrink tubing to prevent the Cree P4 heat from melting the insulation of the wires.
Secure the wires with a rip-tie.
Step 5: Light Up the Cree
For better heat dissipation: fill the pipe with water and close the pipe off with the second end cap.
Warning: the heat from the P4 may expand the water and put pressure on the caps. I haven't experienced any problems with this because the pipe is 1m in length and has enough cooling water.
Step 6: Lens
If you like you can experiment with silicone as well. The picture shows a 1.5cm thick slab of silicone made by filling the bottom of a small bucket with transparent silicone sealant.