This is the last section of the experiment where the actual detection of the resultant diatomic Hydrogen molecules occur. Also the neutral H atom beam created by either photo-detachment via the laser, or by strippng off of gasses within the system.

Here are the drawings for a neutral cup that will be installed soon that will be installed to monitor the neutral H atom beam.

The Neutral cup measures our neutral H atom current. This is done by measuring the secondary electrons that are splashed off by H atoms crashing into a collision plate. The plate is within a tube which will have a positive potential on it (+300-400 V). The secondary electrons are sucked onto this tube and the resulting positive current is read off of the collsion plate. The postitive electrode tube has to be protected by the incident beam, so a grounded shielding tube protects the postive tube from the beam. The cup must be calibrated because with different vacuum conditions the amount of electrons that come off of the collision plate can change. All parts were made of stainless steel.

The length of the positive electrode tube should be at least 2 times the diameter. This cup needs to be calibrated for the number of secndary electrons to incident neutral particles. This ratio is referred to as Gamma. Typical values of Gamma in other designs range from 1 to 1.5.