Emittance Measurements, September 3, 2015

We measured (normalized) emittance and Twiss parameters for the horizontal and vertical planes as a function of momentum (6.7, 7.7 and 8.3 MeV/c).

The results from a previous measurements is summarized in JLAB-TN-14-004 (February 2014): Transverse Beam Characterization in the CEBAF 5 MeV Region

Beam Charge

Cryomodule 0L02 adds the rest of the beam energy. The cavities in 0L02 (7 and 8) are 0.5 meters long. Their "GMES"s are measured in MV/m.

Energy contributed by 0L02, then, is 0.5 * (GMES of cavity 7 + GMES of cavity 8), assuming both cavities are on crest.

Total energy estimate is T_estimate = 500 keV + 0.5 * (GMES-0L02-7 + GMES-0L02-8).

1. Use the above T_estimate formula to determine initial setpoint for MDL0L02 into 5D (bubble chamber) line.

BdL in 5D line [G-cm] = 1412 * T_estimate

2. Make sure 5D horizontal correctors are all set to zero BdL.

3. Send beam and center it on viewers 5D00 and 5D01 by adjusting MDL0L02 and vertical correctors in 0L and 5D region.

4. Once beam is centered on both viewers, use the formula below to determine beam energy -- good ~1%

Beam momentum [MeV/c] = p = (MDL0L02-BdL – 372) / 1412.

Total Energy E [MeV] = SQRT(p² * c² + m² * c⁴) ≈ p * c

Beam Kinetic Energy [MeV] = T = E – mc² ≈ p*c – m*c²

On Tuesday August 11, around 9:30 - 10:05 pm, we tested the bubble chamber sensitivity to gammas with beam (6.3 MeV/c?) to Faraday Cup 2 and 5D line. We did not see any thing on camera, none of the pixels showed any activity, nothing.

These were the beam conditions: