Bunch Numbering

  • View
    38

  • Download
    1

Embed Size (px)

DESCRIPTION

Bunch Numbering. P. Baudrenghien AB/RF for the LHC/RF team. Numerology. For each ring: Convention 1: The 400 MHz RF defines 35640 buckets, spaced by one RF period, and numbered from 1 to 35640 - PowerPoint PPT Presentation

Text of Bunch Numbering

  • Bunch NumberingP. Baudrenghien AB/RFfor the LHC/RF team

    LHCCWG meeting

  • Numerology For each ring:

    Convention 1: The 400 MHz RF defines 35640 buckets, spaced by one RF period, and numbered from 1 to 35640Convention 2: Bucket 1 is the first bucket after the 3 ms long abort gap (defined from bucket 34442 to 35640)

    For 25 ns operation the bunches will occupy buckets 1, 11, 21 etc. with gaps occurring every PS or SPS kicker gap. For 43 bunch operation the bunches will occupy buckets 1, 811, 1621, etc. (see LHC-OP-ES-0003 rev 1.0 for the different schemes).

    LHCCWG meeting

  • For 25ns operation the bunches will occupy buckets 1, 11, 21 etc. with gaps occurring every PS or SPS kicker gap. (see Figure 1 above reproduced from LHC-OP-ES-0003 rev 1.0).

    LHCCWG meeting

  • For 43 bunch operation the bunches will occupy buckets 1, 811, 1621, etc. (see Figure 3 above reproduced from LHC-OP-ES-0003 rev 1.0).

    LHCCWG meeting

  • Revolution Frequency or OrbitFor each ring:The revolution frequency (Frev or orbit) is a train of pulses, with one 5 ns long pulse per turn. This pulse points to bucket 1. The revolution frequency is obtained by dividing the RF by 35640At a given place in the machine, and at a given beam energy (that is fixed RF frequency) the delay between the pulse and the passage of a bunch in bucket 1 will be fixed from run to runDrift during the ramp: Signals remain in phase with the corresponding beam in IP4 (RF cavities). During the acceleration, the revolution frequency increases by 2.2 ppm for protons (868 Hz @ 400 MHz) and 14 ppm for Pb (5.5 kHz @ 400 MHz). [See LHC Radio-Frequency Swing, P. Baudrenghien, 14 th Leade meeting, Dec 15th, 2003]. At a given place, but varying energy (frequency) the Frev-bunch delay will drift during the acceleration ramp due to the difference between signal transmission delay and the beam time of flight. For protons we have 6.5 ps/km, for ions 41.25 ps/km. Not a problem.

    LHCCWG meeting

  • Bunch ClockFor each ring:The Bunch Clock is a square wave obtained by dividing the RF by 10. The divider is synchronized on the Revolution Frequency (see page 8)At a given place in the machine, and at a given beam energy (RF frequency) the delay between the edge of the Bunch Clock and the passage of a bunch will be fixed from run to runDrift during the ramp: During the proton ramp the Bunch Clock frequency increases by 86.8 Hz (protons) and 550 Hz (Pb). At a given place, but varying energy (frequency) the edge will drift with respect to the bunch. (Same figures as for the Revolution Frequency pulses.)

    LHCCWG meeting

  • Collision PatternRing 1 w.r.t. ring 2:While for each ring bucket 1 and its revolution frequency are locked together, the two bunch patterns can be rotated with respect to each other so as to move or set the collision points This is usually done before the injection process with collision (and crossing) points defined before filling. This is the preferred method as it keeps crossing points fixed from injection to physicsIt can also be done after injection by changing the phase of one RF system (and thereby the corresponding beam) with respect to the other (Machine Development)

    Convention 3: bunches in bucket 1 of the two rings collide in IP1 (or any other IP. To be agreed now)

    LHCCWG meeting

  • Clock GenerationAll signals are generated in SR4They are transmitted to CMS (point 5) and BT (dumps) directlyAnd they are transmitted to the other experiments and BI via CCR (optical splitter 1:4)Injection pulses are sent directly to the kickers (not shown above)

    LHCCWG meeting

    text

    text

    Common (Rephasing)

    7 TeV Synth

    400 MHz Ref

    1/10 DividerVTU

    Ref Bunch Clock

    Synchro Module

    Bunch Clock1

    Phase shifter

    TDC

    Cogging

    Cogging of Ref 40 MHz to put it in phase with bunch at 7 TeV: phase shift by 0 to 9 full RF periods at 400 MHz

    To Beam Control system: Rephase both rings onto this reference before physics

    Bunch Clock 2

    SR4

    400 MHz Ref

    Fiber optic links to CCR (AB/CO+EXP), CMS

    (square wave)

    (square wave)

    (square wave)

    (square wave)

    (pulse train)

    (pulse train)

    Fiber optic links to CCR (AB/CO+EXP), CMS

    SR4

    (square wave)

    (square wave)

    VTU

    VTU

    Ring 1

    Ring 2

    1/10 Divider

    RF IN

    OUT

    Sync

    400 MHz RF 2

    F rev 2 (orbit)

    Bunch Clock 2

    F rev 2 (orbit)

    400 MHz RF 2

    400 MHz RF 2

    1/10 Divider

    RF IN

    OUT

    Sync

    400 MHz RF 1

    F rev 1 (orbit)

    Bunch Clock 1

    F rev 1 (orbit)

    400 MHz RF 1

    Fiber optic links to CCR (AB/CO+EXP), CMS

    400 MHz RF1

  • Reference Clock GenerationThe Ref Bunch Clock is a stable, constant frequency square wave at 40.078966 MHz (7 TeV proton) obtained by asynchronous division (1:10) of a 400 MHz Reference (400.789658 MHz). This 400 MHz Reference is generated by a commercial Low Noise Frequency SynthesizerOn the flat top (7 TeV), but before physics starts, the 400 MHz RF1 and RF2 (and the corresponding beams) are rephased onto this 400 MHz Reference. The Bunch Clocks 1 and 2 follow automatically But the Ref Bunch Clock can still be off by 1 to 9 periods @ 400 MHz. To fix that the Ref Bunch Clock will be slowly phase shifted by the proper number of 400 MHz periods to bring it in phase with the bunchWhen physics starts, the delay between the edge of the Ref Bunch Clock and the passage of a bunch will be thus fixed from run to run

    LHCCWG meeting

    text

    text

    Common (Rephasing)

    7 TeV Synth

    400 MHz Ref

    1/10 DividerVTU

    Ref Bunch Clock

    Synchro Module

    Bunch Clock1

    Phase shifter

    TDC

    Cogging

    Cogging of Ref 40 MHz to put it in phase with the bunch at 7 TeV: phase shift by 0 to 9 full RF periods at 400 MHz

    To Beam Control system: Rephase both rings onto this reference before physics

    Bunch Clock 2

    SR4

    400 MHz Ref

    Fiber optic links to CCR (AB/CO+EXP), CMS

    (square wave)

    (square wave)

    400.789658 MHz

    (square wave)

    (square wave)

    (pulse train)

    (pulse train)

    Fiber optic links to CCR (AB/CO+EXP), CMS

    SR4

    (square wave)

    (square wave)

    VTU

    VTU

    Ring 1

    Ring 2

    1/10 Divider

    RF IN

    OUT

    Sync

    400 MHz RF 2

    F rev 2 (orbit)

    Bunch Clock 2

    F rev 2 (orbit)

    400 MHz RF 2

    400 MHz RF 2

    1/10 Divider

    RF IN

    OUT

    Sync

    400 MHz RF 1

    F rev 1 (orbit)

    Bunch Clock 1

    F rev 1 (orbit)

    400 MHz RF 1

    Fiber optic links to CCR (AB/CO+EXP), CMS

    400 MHz RF1

  • Availability of clocks during runssee also edms 628536 v1, TTC System Upgrade, S. Baron, Sept 29, 20051/35640 and 1/10 dividers are resynchronized at each filling, once, before the first SPS-LHC transferDuring resynchronization the output signal disappears for ~1 msSignal presence and validity is then guaranteed, from shortly before filling until beam dumpAfter beam dump it is not excluded that the RF manipulate its equipment (switch a crate off/on) and signal may disappear. Experiments should make sure that no manual reset is needed in that casePresence of signals is not guaranteed outside physics run due to maintenance needed on the RF equipment, or if basic control facilities are lacking. That applies in particular to shutdown periodsThe AB/RF group is responsible for the transmission up to the Fiber Optic receivers installed in the experiments (including on-call service). In return the experiments will make for an easy access to this equipment and help implement remote acquisition of the status of the Fiber Optic RX (optical power, presence and frequency of detected RF signal) so that AB/OP and AB/RF can quickly diagnose the transmission

    LHCCWG meeting

  • Installation planningRF Synchronization equipment being installed/commissioned in SR4Expect all running by mid-April

    LHCCWG meeting

  • RF Synchro: FunctionalitiesSynchronization of the SPS-LHC bunch into bucket transferA train of pulses at the Fiducial Frequency Fc (= FrevLHC/7 = FrevSPS/27 = 1.6 kHz) is sent to the SPS for synchronizationBy displacing this train by x RF periods the transfer will end-up in bucket+x -> Mechanism to select the injection bucket. Transparent to the SPSWe have only one hardware bucket selector for both ringsIt is re-synchronized on two different Frev for the 2 rings -> Mechanism to rotate one ring with respect to the other (before injection)Generation of beam synchronous signals: 40 MHz bunch clocks, revolution frequencies, injection pulses

    LHCCWG meeting

  • This divider will adjust the relative position of ring 2 vs ring 1. It must be adjusted only once at start-upThis sets the RF frequencies before and at injectionBy changing the programmable delay in the bucket selector one chooses the LHC bucket for transfer. It will be adjusted continuously by OP to change the collision point or for multiple-batch injections.This module generates the pulses sent to the injection kickersLHC LLRF RF Synchronization

    LHCCWG meeting

    text

    text

    DUAL FREQ PRGM

    BUCKET SELECTOR

    INJ PULSE GENE

    VTU

    VTU

    F rev prog1

    DDS1

    DDS2

    F rev prog2

    F RF Prog 1

    F RF Prog 2

    WB switch

    WB switch

    Inj. F rev

    F inj

    Ring 1

    Ring 2

    Ring 1

    Ring 2

    Phase shifter

    1/(7 h) divider

    1/h Divider

    RF IN

    OUT

    1/h Divider

    RF IN

    OUT

    Sync

    OUT

    RF IN

    Sync

    Bucket nbr.

    Shifted F inj t