Methods and apparatus for beam density measurement in two dimensions

An apparatus comprising:

• a beam generator configured to generate a beam;
• and
• a beam density measurement system comprising:
• a shield;
• a beam sensor positioned downstream from said shield in a direction of travel of said beam, said beam sensor configured to sense an intensity of said beam, and said beam sensor having a long dimension and a short dimension, and
• an actuator to translate said shield relative to said beam sensor, wherein said shield blocks at least a portion of said beam from said beam sensor as said shield is translated relative to said beam sensor, and wherein measured values of said intensity associated with changes in a position of said shield relative to said beam sensor are representative of a beam density distribution of said beam in a first direction defined by said long dimension of said beam sensor.

A method comprising:

• providing a beam sensor positioned downstream from a shield in a direction of travel of a beam, said beam sensor having a long dimension and a short dimension;
• translating said shield relative to said beam sensor so that said shield blocks at least a portion of said beam from said beam sensor;
• and
• measuring an intensity of said beam with said beam current sensor for different positions of said shield relative to said beam sensor, wherein measured values of said intensity associated with changes in a position of said shield relative to said beam sensor are representative of a beam density distribution of said beam in a first direction defined by said long dimension of said beam sensor.