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Beam Status Report

Niels and Lau. Beam Status Report. NA62 Collaboration Meeting, 27-30 August 2013, Liverpool. The issues observed in the TR. Skew horizontal profiles in the CEDAR region. Some 20% missing K +. Note: no horizontal bends in this part of the beam line!. Alignment issues suspected.

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Beam Status Report

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  1. Niels and Lau Beam Status Report NA62 Collaboration Meeting, 27-30 August 2013, Liverpool

  2. The issues observed in the TR Skew horizontal profilesin the CEDAR region Some 20% missing K+ Note: no horizontal bends in this part of the beam line!

  3. Alignment issues suspected • Remember: We had effectively very little beam time (flooding, vacuum, etc) • We suffered from confusion due to wrong QNR excitation curve (in saturation region) and from H/V inversion in 4-jaw collimators, which onlywas noticed later in the run when we increased the beam acceptance (and size). This took some timeand complicated the interpretationof the observations. • Ideally we would have madeone more full steering iteration,but there was no time left for this(we gave priority to measurements for the experiment). This iterationwill have to be made in the 2014 run. • We suspect some misalignment.

  4. What did we check / consider • We dismounted the roof shielding over the front end and the surveyors checked the alignment of all elements. All was found to be correct. • A special rod was inserted into the TAX and their relative alignment was found correct to better than 1 mm. • We inserted a tool in the TAX and looked at it directly. Also OK to a fraction of a millimeter. • The surveyors checked the alignment of all elements in the front-end from thelocation of the second MTR (which had to be dismounted anyway to be turnedby 180 degrees). They found all correct within about 0.3 mm. • The overall beatch axis was checked (for conceptual bugs in the transformationfrom old to new coordinates) and was found correct. See next slide • A tool was inserted into a ‘fixed’ collimator in T10. A 60 mm diameter insert has a t 20 mm diameter hole, offset. This piece was found to be rotating freely and could have been at any azimuthal angle. This will be fixed correctly next year.

  5. Coherence check of different Beatch axes

  6. Results of measurements in 2013:

  7. Other checks by Niels • Niels has simulated most if not all the imaginable alignment errors withDecay Turtle and all required offsets have been ruled out by the checks described beforehand. • One hypothesis is still somewhat alive. In the confusion between wrong optics (QNR curve) and wrong collimators, we tuned TRIM1 to a wrong current. The suspected 12 Amps mis-tune could lead to an observation like the one we have, but in the opposite direction.There may be a mismatch between the real FISC / collimator direction and the sign convention. However, a check must include the software part of the system and must therefore wait till 2014. • The collimator scans show also an asymmetry but much less pronounced. • Sometimes FISCs show asymmetric profiles even for a nicely symmetric beam.But we have two Fiscs showing the same asymmetry……

  8. So what can we do? • We could not check the alignment of T10 itself. We know that the TBIU ofT10 is off by about 5 mm, due to a mechanical deformation of its support. • T10 itself will be consolidated before the 2014 run: new target box, new monitors, overhaul of all the mechanics. If there was a problem, weshould find it and fix it. • In 2014 we will have to take some time to fully re-tune the beam carefully.

  9. Other open issues for the 2014 run • The double wall separating TCC8 from ECN3 has to be installed and the access system integrated with it. See next slide • The ventilation system upgrade will only be done in 2015, but the pressurization of the double wall and some minimal provisional measures to separate TCC8 from ECN3 will be done before the 2014 run. Also the interlocks on the DP in the air locks at the bottom of PPG853 and 854 will be activated. • Extra money has been obtained to complete the vacuum system. Only the fast valve funding is still an open issue. • The expansion vessel remains to be installed next to the CEDAR. • The H2 infrastructure must be completed. • The TCC8 crane refurbishment is still not guaranteed to be financed. • The access to the dump via the dump tunnel will be fenced off. • Last but not least: a thorough upgrade of CESAR is planned.

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