General Checks¶

Before Measuring¶

Here are a few checks to perform before starting measurements. These are updated as much as possible for Run 3 values.

• Make Sure Intensity Is below \(10^{10}\)ppb until Local Corrections Are In

  After local corrections, we can move to having 3 bunches (each below \(10^{10}\)ppb) evenly spaced along the ring.

• Make Sure The Setup Beam flags are true for Both Beams

  When looking at the LHC Page 1 Vistage, in the "BIS status and SMP flags" section the Setup Beam row should be green (true) for both beams.

• Mask the Appropriate BLMs

  It is possible tp "mask" some of the BLMs, which means making sure they won't trigger any beam dump. They are essentially ignored in the interlocked system when masked.

• Turn Off the Landau Octupoles

  Unless you specifically need them on for your measurements (ampdet & co). These are the MO elements.

• Correct the Machine Chromaticity to a Few Units

  In the past we've used \(2\), which we will most likely keep using in Run 3.

• Mask the ATLAS BCM

  This status should be visible in the Multiturn application (better check still). The only way to change this setting is by contacting the ATLAS control room. See with the EIC to get in touch.

• Check the AC Dipole Keys Are In

  Or MKA if that's used.

• Make Sure the Collimators Are Open

  There should be a pre-made setting for this.

For Measurements¶

Here are some general checks on should always keep in mind when performing measurements.

• Make Sure to Put in the Correct Tunes

  At top energy we're usually at \(Q_x = 62.31\), \(Q_y = 60.32\).

• Start with Small Kicks and Gradually Go up in Amplitude

  For linear kicks we aim for \(\sim 2mm\) in the arcs. The value should be displayed in Multiturn, and after a kick one can directly check the BPM data in the application.

• Use Asymmetrical Deltas for the Driving

  Do not set \(|\Delta Q_x| = |\Delta Q_y|\) for the AC Dipole. We usually go for \(\Delta Q_x = -0.01\) and \(\Delta Q_y = 0.012\). Don't drive on the tune, you don't want to see what happens then ;)

• Have the Losses Applications Open

  When kicking from Multiturn, keep an eye on the losses application for unexpected spikes.

• Make Sure to Log All Info

  Starting in Run 3 a decent amount of automatic logging should be implemented. However, one should always check and make sure to log all relevant information: fill number, location of measurement files etc.

• Analyse as the Data Comes

  As much as possible, let's make sure people analysing the kick data do not fall behind the kickers. If you're a kicker, coordinate with you analyst to stay in sync.

• Give Sensible Names to Complete Sets of Data

  When an analysis is done on a complete group of kicks, try to find a descriptive name. See the info page for naming conventions.

• Log Anything of Interest in the Logbook

  It doesn't hurt to have a lot of information.

General Corrections Caveats¶

• Beware of the Corrections Signs

  For a quick (but rough) reference see this old note this 2022 presentation by Riccardo.

  • Calculated Global Corrections

    The calculated global correction are really corrections and should be trimmed in with a positive sign.

  • Skew Magnets

    All skew magnets are inversed in LSA / MAD-X conventions and the calculated corrections for these should be trimmed in with an opposite sign (that means calculated correction * -1).

  • Triplets

    The triplets are tricky as all three are powered in series with a common knob, then some have an additional trim. Calculated corrections should be sign-swapped for Q1 and Q3 but not for Q2. If creating new knobs is needed, see with the EIC.

  • Local Corrections

    Decide on a convention for how we output the corrections (omc3 or BetaBeat.src) and how to use them? Do checks on friday for that!

• Knob Creation Permission

  It is not enough to be logged in as lhcop to create knobs for corrections. Both Tobias and Ewen have the permissions, if they aren't present see with the EIC and they should be able to give permissions.