Meeting No. 24

Snout for spectrometer B and new angle:

I am working on a design for the He-balloon. Gerhard and I wisited J. Rosche, and we agreed, that it makes sense, that we replace the first two parts of the nose. This way, we can preserve vacuum in the spectrometer B. However, when designing this part I encountered a problem.

Attached plot shows the scattering chamber and present nose of the spectrometer B with the pink color. The while lines are sketches of important angles and other directions. For the ISR, spectrometer B is at 15deg. The exit window is blind for the first 10deg (from beam direction), in order to have enough material to attach the beam-dump. A priori this does not sound problematic, but if one plots everything together, one realizes that the left edge (towards beam dump) of the spec-B window is actually aligned with the left edge of the spectrometer-B's nose.

1.) specB_Nose1.pdf

Hence, if we design a new nose for spec B with big entrance window, the target window will still be in the way! Shell we move B to a slightly larger angle (and loose some of the Q**2), or do we try to find a different solution?

The following plots show the comparison of the rates if the spectrometer B sits at 15.25 and 20.00deg. At 20deg are rates lower for approx. factor 3.

2.) 3.)

The first sketch of a new Nose design at ~20deg is shown here:

4.) specB_Nose2.pdf

Ar-40

I constructed Spectral function for the Ar-40, which should be good enough for estimating rates of the potential experiment.

5.)

The following plots show the kinematic range that we could cover with the A1 setup, combining all three spectrometers.

6.) 7.) 8.)

If we use a liquid 5cm target, the rates would be around 500Hz at 20uA, which fits perfectly into our DAQ. If 10cm gaseous target at 10bar and room temperature would be used, then the rates would be 12.5Hz.

I was talking to Dr. Schilling, who says that it is possible to measure with Liquid Ar, that can be cooled with N2. However, new Heat exchanger needs to be made. Additionally Juergen Diefenbach needs to check how much radioactive Argonne are we producing.

The JLab is running similar experiment right now, but at much smaller rates. Rates are below 1Hz. However, a high statisctics measurement and double polarization measurement, to get a grip on the FSI, they can not do. This is in our reach.
Last modified 24.2.2017