Version 1

**Description of the ACNET devices that control the Main Injector inputs
to the NuMI Beam Permit System**

A. Godley, S. Mishra

<godley@sc.edu>

1/13/2005

1.  **Batch by Batch Intensity Monitor(BBIM)**

**Purpose**:

The BBIM measures the intensity of proton batches in the Main Injector
(MI) on a turn by turn basis. This is achieved by integrating the signal
from a Resistive Wall Monitor (RWM) below MI60. The start and end bucket
of each batch in the MI define gates over which the RWM signal is
integrated to return the intensity. Further, for a given gate the BBIM
will determine if the intensity is above a set threshold after Pbar
extraction, returning a digital logic "Beam/No Beam" signal. This signal
is primarily for the NuMI Beam Permit System (BPS) to ensure that the
Pbar batch (typically the first batch in the MI) has been extracted
before the NuMI kickers fire. The NuMI kicker rise time is longer than
the gap between the Pbar and the first NuMI batch causing the Pbar batch
to be sprayed in the MI tunnel when the NuMI kickers fire if it has not
been extracted.

A BBIM card (reading a single RWM) has two channels, each with 7
integration gates. These gates are ideally set to cover the 6 batches of
MI multi-batch running plus the time frame of the NuMI kicker rise time.
The ACNET device names for the BBIM all begin **I:Bb** where b is the
card number. Currently there is only card 1.

The original design specifications for the BBIM are in Appendix A.

**Master Controls**:

**I:BbC1RF** The BBIM uses an RF signal to determine the bucket size.
This device sets whether an internal (testing) or external (MI) RF
source is used for channel 1.

**I:BbC2RF** As above but for channel 2.

**I:BbC1GA** Gain of Channel 1.

**I:BbC2GA** Gain of Channel 2.

**I:BbDELY** Delay used to offset cable delay of the revolution marker
signal

**I:BbTIME** Timestamp

**I:BbFIFO** Access to the digitized RWM signal

**Baseline Corrector**:

The Baseline Corrector is used to remove the variation in the baseline
RWM signal over an MI cycle in order to calculate the true intensity.

**I:BbBLTH** The threshold is used to set the peak amplitude of the
baseline signal (i.e. when empty buckets are passing the RWM)

**I:BbBLWI** The window is the time width over which the slow
fluctuation of the baseline signal is separated from the peak signal
using a moving average filter.

**I:BbBLMO** Future feature to select between different baseline
correcting algorithms

These baseline corrector and master controls should not need adjusting
once the BBIM has been commissioned.

**Integration gates:**

The following devices define the integration gates. Channel 1 on card 1
will be used as an example (the first two numbers after **I:B** are the
card, then channel numbers.) The gate number 0-6 replaces the **X**:

**I:B11XBE** RF bucket that BEGINS the integration gate.

**I:B11XEN** RF bucket that ENDS of the integration gate.

**I:B11XMN** The number of turns used to calculate the mean intensity.
Typically the mean intensity is not used and this value is left at one.

**I:BbXIN** The returned intensity for fast time plotting.

Table 1 gives the gate settings for multi-batch NuMI/Pbar running. This
set up returns the intensity of the Pbar and 5 NuMI batches, as well as
gate 1 which integrates over the NuMI kicker rise time to determine for
the BPS if beam is present.

  ---------- ----------------- ------------ ------------- -------------- ---------------
  **Gate**                     **Begin                    **End Bucket** 
                               Bucket**                                  

  **\#**     **Description**   **ACNET**    **Default**   **ACNET**      **Default**

  **0**      Pbar batch        I:B110BE     0             I:B110EN       82

  **1**      Kicker            I:B111BE     46            I:B111EN       122

  **2**      NuMI 1            I:B112BE     122           I:B112EN       204

  **3**      NuMI 2            I:B113BE     208           I:B113EN       290

  **4**      NuMI 3            I:B114BE     294           I:B114EN       376

  **5**      NuMI 4            I:B115BE     380           I:B115EN       462

  **6**      NuMI 5            I:B116BE     466           I:B116EN       548
  ---------- ----------------- ------------ ------------- -------------- ---------------

Table 1 Standard set up for the batch integration gates for NuMI/Pbar
running. This example uses channel 1 on card 1, the default, for the
ACNET device names.

**Beam/No Beam:**

The threshold for the NuMI BPS, using Card 1 Channel 1 as an example, is
controlled by the following ACNET devices:

**I:B11BTH** Threshold above which there is considered to be beam in the
gate.

**I:B11BGT** Which gate the threshold comparison is to be made,
typically gate 1.

**I:B11BVA** The beam/no beam signal.

**ACNET Page:**

The BBIM interface is on ACNET page I65, sub-page NUMI EXTRT pages
20-22. Page 20 has the master settings, baseline corrector and beam/no
beams settings. Page 21 displays the gate setup and intensity readout
for the 7 gates of channel 1. This is the primary channel. Page 22 has
the channel 2 gates, which are not yet used.

![](media/image1.png){width="4.333333333333333in" height="6.5625in"}

Figure 1 BBIM master settings on ACNET I65 subpage NUMI EXTRT page 20

![](media/image2.png){width="4.333333333333333in" height="6.5625in"}

Figure 2 BBIM gate settings for channel 1 on page 21, channel 2 is on
page 22

2.  **MI Beam Loss Monitors(BLM)**

**Purpose**:

There are two BLMs in the MI used by the Beam Permit System (BPS),
LMQ608 and LMQ612. These have been instrumented with additional
electronics to provide a signal to the BPS in order to make a decision
on the quality of the beam in the MI before NuMI extraction.

The original design specifications for the BLM electronics are in
Appendix B.

**ACNET Controls:**

The two new BLMs are connected to Chassis 6. They are the only loss
monitors connected to this chassis. These controls are accessed on ACNET
page **E38** sub-page LOSS, pages 4 (reset and hold) and 7 (readout).

**I:LMQ608** Integrated signal (volts) from the loss monitor on
lambertson 61A.

**I:LMQ612** Integrated signal (volts) from the loss monitor on
quadrapole 612.

**I:NLMC6R** Integrator reset. The loss monitor integrators reset a
delayed amount of time after a TCLK event. The delay length is set in
micro seconds and the TCLK event by using the menu A/D -\> Timer
reference.

**I:NLMC6H** Integrator hold. The loss monitor integrators will
integrate until a set time after a TCLK event, then the integrated value
will be held until the next reset. The time is set in microseconds and
the event with the A/D -\> Timer reference menu.

Both the reset and hold are set to \$23, the NuMI beam event. This has a
flat top from 1.19 to 1.26 seconds after the \$23 event. To sample the
losses at flat top, the reset set to 1.22 seconds and the hold to1.23
seconds. This will integrate the losses at the two monitors for 0.1
seconds and hold them till the next sample period begins.

The standard set up for the TCLK, reset and hold are:

  ----------------------- ----------------------- -----------------------
  Device                  Event                   Delay (μs)

  **I:NLMC6R**            \$23                    1220000

  **I:NLMC6H**            \$23                    1230000
  ----------------------- ----------------------- -----------------------

**Signals to the NuMI Beam Permit System:**

The held integrated loss signal is cabled to the NuMI BPS. The level of
loss above which the beam is deemed unsuitable for extraction is set in
the BPS. The time to sample the loss is also set in the BPS (between
Pbar and NuMI extraction). The loss monitor signals at the BPS can be
controlled via ACNET page **E40**, the select module 60A, then \*List
All Channels Menu\* then either channel 0 or 1.

Loss monitor limit:

The upper limit that will cause the permit to drop can be set by
clicking on \*Analog Limits\* and entering the new value. The values
should match that set in Bob Ducar's "The Golden File of NuMI Beam
Permit System Inputs".

As of 12/16/04 these are:

LMQ608 0.5 Volts

LMQ612 0.5 Volts

If a permanent change to these values is made, the person making the
change should ensure that the "Golden File" is updated.

Survey time:

The time that the BPS surveys the loss signal is set by "Associated SAT"
(State Algorithm Table). This should be set to 4 so that the survey is
performed "just before extraction", as defined in Ducar's "Golden File"
document.

![](media/image3.png){width="5.992361111111111in"
height="5.152083333333334in"}

Figure 3 LMQ608 channel page from the ACNET NuMI BPS page E40, max 0.5 V

3.  **MI Orbit Verifier**

**Purpose**:

The orbit verifier consists of 4 MI beam position monitors (BPMs) and
additional read out electronics that send position signals to the NuMI
Beam Permit System (BPS). The BPS then determines if the beam position
is within the desired orbit before NuMI extraction (but after Pbar
extraction).

The original design specifications for the orbit verifier are in
Appendix C.

**ACNET devices:**

  ------------ -------------------- ----------------- ---------------------
  **BPM**      **MI Device**        **Orbit           **Orbit Verifier
                                    Verifier**        MADC**

  H606         I:HP606              E:OHP606          I:HP606N

  H608         I:HP608              E:OHP608          I:HP608N

  V607         I:VP607              E:OVP607          I:HP607N

  V609         I:VP609              E:OVP609          I:HP609N
  ------------ -------------------- ----------------- ---------------------

The position signal E:OHPXXX should be identical to the I:HPXXXN signal
seen by the MADC of the BPS. The E:OHPXXX position signals are displayed
on ACNET page **E38** sub-page BPMS, page 3.

**Signals to the NuMI Beam Permit System:**

The Orbit Verfier inputs to the BPS are controlled through ACNET page
**E40**, then click module 60A, then click \*List All Channels Menu\*
then the required channel 54 to 57 for the position signals, (the unused
intensity signals are 59-62).

Position limit:

The limits outside which the permit will drop can be set by clicking on
\*Analog Limits\* and entering the new values. The values should match
those set in Bob Ducar's "The Golden File of NuMI Beam Permit System
Inputs", which are reproduced in Table 2 below. The values are set +/-
3mm around the central value, this may be reduced later. (12/16/04)

If a permanent change to these values is made, the person making the
change should ensure that the "Golden File" is updated.

Table 2 Orbit Verifier default orbit limits UPDATED 12/16/04

  ---------------- ---------------------------- --------------------------
  **BPM**          **Lower Limit (mm)**         **Upper Limit (mm)**

  HP606            -2                           4

  HP608            -25                          -19

  VP607            2                            8

  VP609            -4                           2
  ---------------- ---------------------------- --------------------------

Survey time:

The time that the position is surveyed is set by "Associated SAT" (State
Algorithm Table). This should be set to 4 so that the survey is
performed "just before extraction", as defined in Ducar's "Golden File"
document.

![](media/image4.png){width="4.333333333333333in"
height="4.395833333333333in"}

Figure 4 Sample Orbit Verifier page

APPENDIX A

**Specifications for a batch by batch intensity monitor for the**

**Main Injector**

Andrew Godley

University of South Carolina

godley@sc.edu

Integration gates 500-1600ns

Minimum time between batch windows 3 buckets \~55ns

Time between pbar and numi batches 43 buckets \~800ns

Two main integration gates:

Batch (83 x 18.8ns) 1560ns

NuMI Kicker rise time 1300 - 1500ns

Maximum rise/fall of gate 10ns

Trigger off beam synch

Placement of gates 1 Pbar batch Bucket 0

(Synched with RF) 2 1500 ns before NuMI Batch 1

3 NuMI batch 1 Bucket 122

4 2 208

5 3 294

6 4 380

7 5 466

8 Possible 6th NuMI batch

Gates 1 and 8 are mutually exclusive, so there will only ever be 7
possible gates in a given MI cycle.

Sampling Frequency 20 turns

Maximum intensity per batch 1.5 10^13^

Minimum intensity per batch 10^11^

Resolution and calibration on absolute 3%

max intensity

Resolution on absolute min intensity 10%

Resolution on relative near maximum 3%

intensity (batch to batch and

sampling to sampling)

**Controls**:

The ability to set the position of gates, no more frequently than a MI
cycle, is needed. This will be achieved by sending the beam RF and a
digital signal with the first and last buckets for the gate.
Alternatively, a separate module could provide start and stop signals.

The minimum threshold for the threshold digital output signal below
needs to be a changeable input.

**Outputs**:

7 Channels giving a signal suitable for fast time plots at 720Hz

**Threshold Digital Output:**

(This is the "beam/no beam" signal for the NuMI Beam Permit System)

Need a signal that to feed directly into the digital input of a CAMAC
C200 module. Signal is normally TTL high, goes to low for at least 3.5 s
if beam is present after extraction. Permit will be dropped by BPS
system upon receiving this signal.

Create signal by an AND of:

MIBS \$79 plus a delay (Pbar kicker firing plus delay to ensure
integration has

occurred after extraction)

Intensity from integration window above/below threshold (beam present
after

extraction attempt?)

Nominally, this signal is only needed for gate 2 as listed above.

**Useful References:**

Gated Current Integrator for the Beam in the RR Barrier Bucket, C Bhat,
A. Ibrahim. Beams-doc-745-v1

A Multi-Batch Fast Bunch Integrator for the Fermilab Main Ring, G. Vogel
et al, BIW98

**Position**:

The system should preferably be in MI60, ie close to the NuMI BPS.

**Approximate intensity numbers and Resistive Wall Monitor(RWM)
signals:**

1 Booster turn gives 4.4 10^11^ protons in a MI batch =\> \~35mV bunch
peak from RWM

12 Booster turns gives 5 10^12^ protons \~400mV bunch peak from RWM

![](media/image5.png){width="5.0in" height="4.139583333333333in"}

Figure 5 Bunch structure and a 5 bucket gap between batches, measured
with the RWM

![](media/image6.png){width="5.0in" height="4.004861111111111in"}

Figure 6 RWM measurement of the multi batch structure with the PBar
batch being isolated by larger gaps (\~43 buckets)

![](media/image7.png){width="5.0in" height="4.004861111111111in"}

Figure 7 Expanded measurement of the multi batch structure during 3
turns with the RWM. The varying baseline is evident.

![](media/image8.png){width="5.0in" height="4.2444444444444445in"}

Figure 8 Varying baseline of the RWM during multi batch mode.

![](media/image9.png){width="5.0in" height="4.004861111111111in"}

Figure 9 Toroid measurement of the multi batch structure. The signal is
unable to return to its baseline before the next batch arrives.

APPENDIX B

**MI beam loss monitor signals for the NuMI Beam Permit System**

Andrew Godley

University of South Carolina

<godley@sc.edu>

**Introduction**:

These specifications describe read out electronics that will provide
loss signals from the MI Beam Loss Monitors in the NuMI extraction
region. Their purpose is to create analog loss signals for the NuMI Beam
Permit System to determine if losses are below the acceptable limit.
This determination by the BPS is to be made in the 1ms between PBar and
NuMI extraction.

**Loss ranges** 0.01 - 10 rad/s

Signals going above range should hold at the max output signal voltage.

**Resolution on loss** 0.01 rad/s

**Outputs**:

An analog loss signal suitable for a fast time plot at 720Hz is
required. The output loss signal should be the integrated loss over a
variable gate starting shortly after the \$79 trigger of the PBar
kicker, and ending in 20 to 40 turns. Thus, the signal will be updated
once per MI cycle.

This analog output will go to the Process Channel Interface which in
turn connects to a C204 module of the NuMI Beam Permit System. The PCI
also connects to an MADC and from here can be sent to ACNET for fast
time plotting. The signal should range no more than ±10V.

**Inputs**:

Delay between \$79 and start of the integration gate.

Number of turns to integrate over.

**Timing**:

The BPS takes 200 micro seconds to drop the permit after the loss signal
goes above the limit. There is 1000 micro seconds between the PBar and
NuMI extractions. Therefore the signal must be generated well within 800
micro seconds of PBar extraction.

**Location**:

The electronics will be in MI-60. Two new BLMs dedicated to the BPS will
be added. One will be in the 608 region, the other near Q612.

**Signals**:

Sample plots from the MI monitor LM 607B follow. Peak losses shown are
on the order of 30 mrad/s. Signals from the LM were amplified with
MechTronics model 500 R C amplifier. Gain was at its maximum of 512. In
all plots, the purple trace is the loss signal, and the blue trace is
the intensity signal from a nearby BPM RF module, used to indicate the
presence of beam.

Figure 1 High loss at
injection![](media/image10.png){width="5.999305555555556in"
height="4.499305555555556in"}

![](media/image11.png){width="5.999305555555556in"
height="4.499305555555556in"}

Figure 2 Signal has rise time \~2 microseconds

![](media/image12.png){width="5.999305555555556in"
height="4.499305555555556in"}

Figure 3 Injection and subsequent two turns

![](media/image13.png){width="5.999305555555556in"
height="4.499305555555556in"}

Figure 4 Identical signal as figure 3 after integration by the amplifier

APPENDIX C

**MI beam orbit verifier specifications for the NuMI Beam Permit
System**

Andrew Godley

University of South Carolina

<godley@sc.edu>

**Introduction**:

These specifications describe read out electronics that will provide
position signals from the RF modules attached to the MI Beam Position
Monitors in the NuMI extraction region. The purpose of these electronics
is to create an analog position signal of the beam in the MI so the NuMI
Beam Permit System can determine if it is within 2 mm of the desired
orbit. This determination for the BPS is to be made in the 1ms between
PBar and NuMI extraction.

**Working batch intensity range** 3 10^11^ to 1.5 10^13^

The lower intensity limit is during NuMI commissioning. During NuMI
running, the batch intensity should range from 5-10 10^12^

**Position range** ±30 mm

**Three sigma resolution on position** 0.5 mm

This resolution limit is to be applied at the typical NuMI intensity,
and within ±5mm of the desired orbit.

**Outputs**:

An analog position signal suitable for a fast time plot at 720Hz is
required. The intensity signal from the BPM can be used by the read out
electronics to gauge when beam is present. The output position signal
should then be an average of the BPM position signal when beam is
present**.** Hence before PBar extraction, the signal will be an average
of all six batches, and after an average of the 5 NuMI batches. The
average will be taken over a maximum of 10 turns.

This analog output will go to the Process Channel Interface which in
turn connects to a C204 module of the NuMI Beam Permit System. The PCI
also connects to an MADC and from here can be sent to ACNET for fast
time plotting. The signal should range no more than ±10V.

**Inputs**:

Beam synch as a signal of the start of each turn

**Timing**:

The BPS takes 200 micro seconds to drop the permit after the position
signal goes out of range. There is 1000 micro seconds between the PBar
and NuMI extractions.

**Location**:

In MI-60, connecting to HP608/606 and VP607/609

**BPM scale factors:**

Horizontal : Pos(mm) = 0.232 V^5^ + 0.153 V^3^ + 5.839 V

Vertical: Pos(mm) = 0.297 V^5^ + 0.673 V^3^ + 8.462 V

V is BPM signal in Volts. A monitor output signal is available at the
front of the RF modules with a 20dB attenuation from the voltage used in
the above scales.

Sample BPM signals (from the monitor output of HP604):

![](media/image14.png){width="5.0in" height="4.2444444444444445in"}

Figure 10 Position signal of the PBar batch at injection. The dark line
represents the intensity signal from the BPM and indicates when the
batch is passing through it. The position is given as the voltage
relative to ground (marked by the 2) and is only relevant when beam is
present.

![](media/image15.png){width="5.0in" height="4.2444444444444445in"}

Figure 11 Position signal in the middle of the MI cycle. The position
signal is now constant as the batch passes through the BPM.

![](media/image16.png){width="5.0in" height="4.004861111111111in"}

Figure 12 Position signals from the end of the MI cycle. The signal is
still constant. The position is given relative to ground, marked by the
2 on the left scale.

![](media/image17.png){width="5.0in" height="4.004861111111111in"}

Figure 4 BPM signals in multibatch mode, the PBar batch and the 5 NuMI
batches can be seen. The pink trace is the beam intensity. It is a
downward going signal, from its ground marked by the 3 on the left side
axis. A turn starts at the end of the first time division. The intensity
signal drops to indicate the presence of the PBar batch, then rises
again during the \~40 bucket gap. It then drops again for the 1^st^ NuMI
batch. The intensity signal does not have time to return to ground in
the \~5 bucket gap between NuMI batches. Four more NuMI batches follow,
then a second turn starts just after the 6^th^ time division. The blue
trace is the position. The position is seen to be constant from batch to
batch. The position signal does not have time to return to its baseline
in between batches.