May 31st

(return)

Attempt to setup pion beam. Not successful.

1. In the standard pion optics the GTH2QD21 should be 0. Unfortunately, during translation from MIRKO to LSA, this zero changed into 1e-4, while the magnet has negative polarity, so setting up the machine with standard optics gives error. To be corrected in LSA.
2. For the pion part I have tried to use settings from IBHS saves from 2014. Unfortunately for the high-rigidity pions the values for the magnets are outside the maximum ranges. Not much but still. Probably the maximum alowed ranges were slightly larger in 2014 (it is possible!).
3. The standard optics comes from Sebastian Ratschow and has large BETX in TH2QD21/HADQD12 region. I had 2.5 GeV proton beam and the emittance was large enough to give losses on the aperture. I have optimized steering, but the losses were still substantial (radiation alarm inside HHT cave). Installation of larger chambers in TH2QD21/22, foreseen for this shutdown, is actually very important to minimize these losses.
4. HADES wants to run pions in 2021. They say that they don't care if protons are used or argon/nitrogen. If this is the case: don't use protons. I had 1e9 protons per spill and I could not see anything on most screens. Especially tricky would be hitting the pion target, because this screen has bad sensitivity, so maybe even with 1e10 protons per spill you won't see anything. The gas-grids are OK, but GHADDG1G seems to have lower sensitivity then the previous two. Action: ask BI.
5. Sebastian's optics should work, but it is quite aggressive in terms of the transverse beam size in TH2 region. I would give it a try and optimize it a bit better, with smaller BETX at TH2QD2 magnets.

Beam loss profile for old optics (standard):

Beam loss profile for Sebastians optics:

The difference between the two above can be clearly understood from their beta-functions behaviour.