Slits

What

Slits are devices we use to control beam size, limit beam intensity, and select for specific charges

There are 4 slits per set, a top, bottom, left, and right slit. The top and bottom are used for beam intensity while the left and right are used for charge selection, we do not change the left and right slits.

Where

There are 4 sets of slits in FRIB, one for each of the sources, one by the end of the FSEE beam line, and one for the charge selector. We only use adjust the source slits.

Control them via the Source Pages or Front End Diagnostics

K500 also has source slits for its one source

does ReA have slits

How

Slits can be set manually to any given position, measured in mm from being closed, 40mm represents the maximum of what we normally use

Slits being fully closed would be 0mm, 0mm, 0mm, 0mm. Slits being as open as we would set them would be 40mm, 40mm, 40mm, 40mm

HPECR slits in FRIB can also be controlled by setting the Vertical Gap and Center, again, do NOT change the horizontal slits

Why

Source Physicists appreciate regular Slit Scans, which can be found under Physics Apps.

We should also appreciate them, you can always load old Slit Scans to see what portion of beam you're actually cutting

Pictured below is an example of a Slit Scan, the greyed out portion represent beam that's currently being blocked by the slits

Generally the slits should be centered on the peak of the desired charge state, as shown below

The left represents the tail end of our desired peak, you can tell as it has an appreciable slope, including more of this, i.e. opening the slits farther left in this instance, will increase beam loss along the accelerator

The right lacks the same severe slope, and thusly is “safer” to include

Regardless, the area under curve between the slits should be proportional to the amount of beam sent