Gamma Spectroscopy Castle

Print-in-place gamma spectroscopy castle to be filled with lead shot.  Cylindrical 100x100mm internal volume.  3cm of shielding, which provided me a 93% reduction in background gamma count rate.  Includes a cable passthrough, optional magnetic scintillator mount, and optional magnetic AlphaHound ABG case.  No hardware, glue, or lead handling beyond pouring shot into the castle.  Optimized for cost: #9 birdshot is the smallest diameter available cheaply, and is frequently sold in 22lb units.

THIS REQUIRES A LOT OF LEAD.  ASSEMBLE A CLEANABLE WORK SURFACE.  WEAR GLOVES AND A MASK.  WASH YOUR HANDS.  NO KIDS ALLOWED.

Required Items:

1. 1ft USB-C cable: female to 90-degree male.  Cable may be no more than 4.5mm diameter (remove decorative woven sheathing if necessary).  Female end no more than 12mm wide.

2. 44lbs of #9 lead birdshot

3. (optional) 12x 9x4mm neodymium magnets 

Castle Body, Castle Lid:
Print 1 each.  These parts have integrated supports that should not be removed.  No other supports are necessary.  These integrated supports require a 0.68mm extrusion width, and 0.25mm layers.  Print with plain old PETG, as CF and other additives may weaken layer bonding.  4 perimeters, 4 top and bottom layers, and 20% gyroid infill.

Castle Body - Closure, Castle Lid - Funnel, (optional) ABG Castle Case:
Print 1 each.  No supports are necessary.  Use plain old PETG, as CF and other additives may weaken layer bonding.  4 perimeters, 4 top and bottom layers, 20% gyroid infill.

Cable Passthrough:
Print 4.  No supports are necessary. Use 95A TPU, 4 perimeters, 4 top and bottom layers, 20% gyroid infill.

Assembly: 

1. Fill the Castle Body with #9 lead shot.  Pause to tilt and shake repeatedly throughout: the goal is to fill all voids and pack the shot as tightly as possible, especially beneath the shielded chamber.  Take your time: the more you shake, the more will fit, and the better the shielding will be.  Stop when shot is level with the angled supports. 

   

2. Gently snap the Castle Body - Closure into place, working your way around the periphery.  Ensure no shot is on top of the angled supports. 

   

3. Place the Castle Lid upside down on top of the Castle Body assembly. Insert USB cable through the Castle Lid such that 150mm of the male end is pointed up.  Interlock 2 Cable Passthroughs around the cable, and press them into the Castle Lid.  These parts must contain the weight of the lead shot, so they're a tight fit: carefully and firmly press them towards the cable, and down into the Castle Lid.  These parts have a chamfered edge to make insertion easier.  The Cable Passthroughs will index into place once flush with the Castle Lid.

   

   

4. (optional) Press 6 magnets into the underside of the Castle Lid.  Recommend marking their polarity.  

   

5. Invert the Castle Lid assembly such that it inserts into the Castle Body.  Insert the Castle Lid - Funnel: this part has a cutout for the USB cable.  Fill with the remaining #9 shot, again pausing frequently to tilt and shake the part.  Go slowly, shake frequently, and you'll be surprised how much will fit.

   

6. Again seal the USB cable to the Castle Lid using 2x Cable Passthroughs.  See notes above.  Ensure Cable Passthroughs are flush with the Castle Lid.

   

   

1. (optional) press-fit 6 magnets into the AlphaHound ABG Castle Case.  Double-check their polarity: this part should magnet firmly to the Castle Lid assembly.  A cable cutout is provided such that the ABG Castle Case assembly can neatly magnet into place. 

   

:)