1. Crossing angle and polarity first aid
ALICE and LHCb
Crossing angle and polarity first aid
ALIC and LHCb angle and polarities - JW
21/2/2011

2. Angles, knobs, polarities
Experiment
Xing angle* (mrad)
Energy (GeV)
ALICE
1077
450
138
3500
LHCb
2106
270
(*) full xing angle corresponds to twice those values.
Nominal values.
ALIC and LHCb angle and polarities - JW
KNOB full field (injection, KNOB = xing angle with FIDEL calibration):
ALICE: KNOB = mrad I = 6000 A
LHCb: KNOB = mrad I = 5850 A
Experiment
Polarity
Sign of internal Xing angle
ALICE
Positive
Negative
LHCb
21/2/2011

3. ALICE polarities and crossing angles
Superposition of the external and internal Xing angles can be compensating (opposite signs) or additive (same signs).
External Xing
Polarity
Internal Xing
Net effect
Positive
Negative
Compensation
Addition
ALIC and LHCb angle and polarities - JW
For 2011 high intensity proton running, the configurations where the internal and external angles add up must be used (magenta).
21/2/2011

4. LHCb Example of the LHCb spectrometer bump corresponding to:
ALIC and LHCb angle and polarities - JW
Spectrometer
Example of the LHCb spectrometer bump corresponding to:
NEGATIVE internal Xing angle (B1 moving inwards),
POSITIVE spectrometer kick (B1 kicked outwards),
POSITIVE spectrometer PC POLARITY.
21/2/2011

5. LHCb polarities and crossings
External Xing
Polarity
Internal Xing
Net effect
Positive
Negative
Compensation
Addition
ALIC and LHCb angle and polarities - JW
For 2011 high intensity proton running, the configurations where the external angle is negative will be used (magenta).
For positive polarity the internal angle adds to the external angle – the preferred configuration (for us).
For negative polarity the internal angle partly compensates the external angle.
21/2/2011

6. Spectrometer bump in MADX
LSA K: refers to the ratio of magnet kick / crossing angle.
In 2010 the magnet calibration curves were revised (FIDEL team).
In RED the nominal crossing angle at 7 TeV
Exp
Magnet
MADX Kick
(murad)
LSA K 2009
(murad/murad)
LSA K 2010 (murad/murad)
ALICE (V)
abxwt.l2
-1.104
70 murad
abwmd.l2
+2.104
abaw.r2
-1.908
abxwt.r2
+0.908
Sum kick
-0.027
LHCb (H)
abxws.l8
-135 murad
abxwh.l8
ablw.r8
abxws.r8
0.0099
ALIC and LHCb angle and polarities - JW
21/2/2011

7. Contacts Magnet Person Group ALICE spectrometer Xavier Pons PH/DT
Exp. Magnet contacts:
Magnet
Person
Group
ALICE spectrometer
Xavier Pons
PH/DT
LHCb spectrometer
Nicolas Bourgeois
ALIC and LHCb angle and polarities - JW
21/2/2011