> Fermilab/BD/TEV
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> Beams-doc-1018-v1

February 12, 2004

Version 1.0

Implementing Fixed Back Porch Time

on the Tevatron Energy Ramp

Mike Martens

Fermilab, Beams Division, Tevatron Department

## Abstract

[Title:]{.underline} Implementing a Fixed Back Porch Time on the
Tevatron Energy Ramp

[Author:]{.underline} M. Martens

[Date:]{.underline} February 12, 2004

[Category:]{.underline} Tevatron sextupole (b2) field drift.

[Goal:]{.underline} Recent MTF measurements of the b2 drift in the
Tevatron dipole magnets demonstrate that the amount of b2 drift on the
front porch is a function of the time spent on the back porch after
decelerating from flattop. Presently the time spent on the back porch is
not well controlled because the "Decelerate" and "Goto Injection Porch"
aggregates of the sequencer are run separately. A new sequencer
aggregate "Decelerate, Goto Inj Porch" has been developed which provide
a consistent back porch time for all Tevatron shot setups.

# **Aggregate implementation:** 

The new "Decelerate, Goto Inj Porch" aggregate was implemented on
February 9, 2004. The back porch time is 96 seconds (= 90 seconds after
a \$44 event + 6 seconds to start the reset portion of the Tevatron
ramp.)

# 

# **Aggregate checkout:**

On January 26^th^, while the Tev was down for repairs, the updated
aggregate was tested without beam and ready for use. A run through of
the Tevatron shot setup sequence with the new aggregate in place of the
existing "Decelerate" and "Goto Injection Porch" aggregates was
performed. Monitor devices such as separators, b2 drift compensation,
etc. and compare to C23 files to verify devices are at their proper
settings.

# **Notes on the Back Porch Time :**

During the aggregate checkout the relative timing of various clock
events were recorded and are shown in the table below.

  ----------------- ------------- ------------- ------ ---------- --------------
  **Description**   **TCLK        **Time in            **Total    **Time
                    event**       SC**                 time**     difference**

  DFG Continue      \$63          33.25728      0      33.25728   

  Start of          \$6D          41.25573      0      41.25573   7.998453
  decceleration                                                   

  Start of BP       \$44          4.876218      120    124.8762   83.62049

  DFG stop          \$62          6.876222      120    126.8762   2.000004

  DFG continue      \$63          37.45923      180    217.4592   90.583

  Tev Reset         \$41          3.003353      240    243.0034   25.54413

  Start of FP       \$43          7.25648       240    247.2565   4.253127

  DFG stop          \$62          9.256486      240    249.2565   2.000006
  ----------------- ------------- ------------- ------ ---------- --------------

A summary of events in the new aggregate:

-   Tev at flattop.

-   Sequencer issues the \$63 to start the Tevatron ramping.

-   Event \$6D triggers 2 seconds after \$63. This marks the start of
    the down ramp.

-   Event \$44 triggers 83.57 seconds after the \$6D. This marks the
    start of the BP. The TCHROM OAC also reacts to the Event \$44 and
    marks the start of the back porch time.

-   Event \$62 triggers 2.0 seconds after the \$44. This stops the Tev
    ramp.

-   The sequencer waits 90 seconds after event \$44 then SETS_SEQ STATE
    22 (Tev Reset).

-   The TCHROM OAC reacts to the state change to Reset and loads the
    front porch curves for the b2, tune, and coupling compensations. The
    time on the back porch (the time since the Event \$44) is used for
    the BP time and used in the b2 algorithm. This time is recorded in
    the TCHROM log (OACTCHRM on D112.)

-   The sequencer waits for T:CHRLST to indicate the front porch tables
    were properly loaded.

-   The sequencer triggers event \$63 to start the Tev ramping.

-   6.12 -- 2.0 = 4.12 seconds after the \$63, the Tev starts to ramp
    down to 90 Gev.

-   The sequencer waits for the Tev bus to reach 400 amps, waits for 4
    seconds, then triggers the \$41 event.

-   Event \$43 triggers 4.25 seconds after the \$41 event and marks the
    start of the front porch. This also triggers TCHROM to mark the end
    of the back porch and the start of the front porch. The time
    difference between the start of the front porch and the start of the
    back porch is calculated and loaded into T:BPTIME by TCHROM. (See
    note below.)

-   Event \$62 triggers 2 seconds after the \$43 event and stops the
    Tevatron ramp.

-   The Tevatron is now on the front porch at 150 Gev.

There are actually three separate times associated with the back porch.

1)  This first is the time from the start of the back porch till the
    time that TCHROM detects the transition of V:CLDRST to RESET. This
    is the time used by THCHROM in the algorithm to calculate the front
    porch chromaticity corrections.

2)  The second is the actual time at 150 Gev on the back porch. This is
    the above time, plus a delay for the sequencer to issue the \$63,
    plus 4.12 seconds after the \$63 event is triggered before the Tev
    starts its ramp down.

3)  The third is the time from the start of the back porch to the start
    of the front porch. This is the time recorded in T:BPTIME.

These are recorded in the table below for the test of the new aggregate.

  ----- ---------------------------------- --------------------------------
  1\)   TCHROM log BP Time                 89 seconds

                                           

  2\)   (Event \$63 + 4.12) -- Event \$44  96.7 seconds

                                           

                                           

        TCHROM log BP Start Time           1075119539 seconds

        TCHROM log BP End Time             1075119661 seconds

        TCHROM log FP Start Time           1075119661 seconds

  3\)   T:BPTIME                           122 seconds
  ----- ---------------------------------- --------------------------------

# ***Decelerate, Goto Inj Porch*** **Aggregate** 

This is a listing of the new aggregate used on Jan 26^th^, 2004.

TV Window \'Decelerate, Goto Inj Porch\'

::: CHECK_DEVICE C:LBSEQ READING .

::: KILL_BEAM TEVATRON .

::: CTL_DEVICE T:PBKTC RESET .

::: CTL_DEVICE T:ABKTC RESET .

::: COG ABSOLUTE 0 .

::: SET_DEVICE T:FWLATT 0 .

::: SET_SEQ FILE 22 .

::: ACL DAMPER_OFF .

::: ACL HORZ_DAMP_OFF D

::: SET_SEQ FILE 13 .

::: SEQ_PGM REQUEST vsa collider .

::: SET_ENUMERATED V:TEVMOD .

::: SET_DEVICE V:SDAENB 2 ?

::: SET_DEVICE V:SDAENB 1 ?

::: SET_DEVICE V:SDAENB 1 D

::: SET_DEVICE V:TUNEUP 1 .

::: SET_DEVICE V:RHCNT 0 .

::: FTP decelerate 0 .

::: FTP b2 plot 0 .

::: SET_SEQ FILE 8 .

::: TIMER T:TD6D DECELERATE .

::: NOTIFY deceleration .

::: SET_SEQ STATE 19 .

::: WAIT_STATUS T:CHRLST .

::: EVENT 63 TRIGGER .

::: WAIT_FOR EVENT 62 .

::: SET_SEQ FILE 17 .

::: SET_SEQ STATE 20 .

::: LEAD_FLOW OFF HIGH .

::: CHECK_DEVICE C:LBSEQ READING .

::: EVENT C7 TRIGGER .

::: WAIT_DEVICE C:LBSEQ .

::: EVENT D4 TRIGGER .

::: NOTIFY backporch .

::: EVENT 46 TRIGGER .

::: REPLAY C49 reloadafterstore .

::: FTP b2 plot 0 D

::: FTP b2 correct 105 .

::: WAIT_FOR EVTSEC 44 + 90 .

::: SET_SEQ STATE 22 .

::: WAIT_STATUS T:CHRLST .

::: EVENT 62 ENABLE .

::: EVENT 43 ENABLE .

::: EVENT 63 TRIGGER .

::: WAIT_DEVICE T:IPROG .

::: WAIT_FOR SECS 4 .

::: EVENT C1 ENABLE .

::: EVENT 41 TRIGGER .

::: EVENT C1 DISABLE .

::: WAIT_FOR EVENT 62 .

::: SET_SEQ FILE 50 .

::: POLARITY C:B0SHP PLUS .

::: POLARITY C:B0SVP MINUS .

::: ABORT_MASK ALL_TEV DISABLED .

::: SET_SEQ FILE 48 .

::: EVENT 74 TRIGGER .

::: SET_SEQ FILE 52 .

::: SET_SEQ RUN +=1 .

::: ACL WAIT_FOR_READING_MATCH ?

::: SHOT_LOG Chapter ?

::: SHOT_LOG COMMENT ?

::: SET_SEQ STATE 1 .

::: ACKNOWLEDGE .

::: ACL SET_C49_DEVICES .

ERR SEQ_PGM REQUEST C23_front_por .

::: NOTIFY front porch .