# Presentation: 492219

## The status of transverse and longitudinal damper system in MI

**               ****September 18 2003**
**   ****MINOS collaboration meeting**
**               ****Hyejoo Kang**
**            ****Stanford University**

## 1. Overview of the damper system2. First attempt to implement features of the damper system for NuMI.3. Damper system transverse  measurement4. Multi-batch studies with the transverse damper operating5. Status of longitudinal damper 

- 1. Overview of the damper system2. First attempt to implement features of the damper system for NuMI.3. Damper system transverse  measurement4. Multi-batch studies with the transverse damper operating5. Status of longitudinal damper

## Generic damper: need to consider phase shift and time delay of the beam when it reaches the kicker

*All Logic*
*Inside*
*FPGA*

**Purpose of dampers :  to reduce oscillation amplitude in trans. and long. caused by  injection error etc**

- Generic damper: **need to consider phase shift and time delay of the beam when it reaches the kicker**

## All coordinate digital Damper for MI

- 53 MHz, TCLK, MDAT,...

- Monster
- FPGA(s)

- Minimal
- Analog
- Filter

- FAST
- ADC

- Stripline
- Pickup

- Minimal
- Analog
- Filter

- FAST
- ADC

- 14

- VME

- 106 / 212 MHz

- Stripline
- Kicker

- Power
- Amp

- Minimal
- Analog
- Filter

- FAST
- ADC

- Resistive Wall Monitor

- Broadband Cavity

- FAST
- DACs

- > 27 MHz

- FAST
- DACs

- Power
- Amp

- Transverse
- Dampers
- Identical
- X & Y

- Longi-
- tudinal
- (Z)
- Damper

- 2-10

- 2-10

## 212 MHz Sampling of  RWM signal using the longitudinal damper

***2*D-(C+E) gives intensity***
***By adding the bunch intensity of all bunches in a batch we can also measure the beam intensity***

## Longitudinal Damper FPGA Logic

**ResistiveWall Pickup**

- ADC

- 14

- Synchrotron
- Motion
- Velocity
- Filter

- Bunch-by-
- Bunch Digital
- Phase Detector

- +THREH

- -THRESH

- Multi-Turn
- Memory

- Bunch Intensity
- FIR Filter

- +THREH

***Individual Bunches are kicked + or – depending on whether they are moving right or left in phase***

**8 turns for weighted calculation **

**Will be implemented**

## Repetitive 212 MHz sampling of stripline signalcontains bunch-by-bunch phase and amplitude

***“******A - B”  gives bunch-by-bunch “in-phase” signal***
***:amplitude***

***Vector Sum ***
***sqrt(I**2 +Q**2)  is insensitive to clock jitter***

***“******D - (C+E)/2”  gives ***
***bunch-by-bunch “out-of-phase” or “quadrature” signal***
***:phase***

## Three-Turn Filter for Transverse Damper

**Three-Turn Filter for Transverse Damper**

**    ****Damper kick is calculated from single BPM position reading on 3 successive turns.**

## Raw  Waveform  for Undamped, Damped and Anti-Damped Bunches (transverse)

## Implement firmware code for the damper system to measure beam intensity of each beam batch using the long. Damper:    special feature for NuMI

- -- NUMI Signal Accumulator control pulses
- ()=NUMI_BB1: dff(.clk=adclkby2, .d=bucket_count.q[]==reg_DDZBB1.q[]);
- -- pulses on bucket to capture for ACNET
- ()=NUMI_BB2: dff(.clk=adclkby2, .d=bucket_count.q[]==reg_DDZBB2.q[]);

- Begin the bunch intensity measurement at bunch DDZBB1 (numbered relative to DDZBK0 )

- End the bunch intensity measurement at bunch DDZBB2 (numbered relative to DDZBK0 )

- DDZBK0: (ACNET device)
- --> set this variable equal to the first bucket

## Works fine with one batch

- --------------------------------------------------------------------------------------
- -- accumulators big enough to width allows >588 accums w/o overflow.
- -- Reset once per turn at bunch programmable via NUMI_BB1
- --  via ".sload" port which loads first sample (instead of adding it in)
- ()= NUMI_accI : altaccumulate (.clock=adclkby2, .sload=NUMI_BB1,
- .data[] = Ich0.q[])	 with (WIDTH_IN=16, WIDTH_OUT=26, LPM_REPRESENTATION="SIGNED") returns(.result[0]);
- -- Output holding registers to capture I totals up to at end of each turn for ACNET display
- -- holding registers for VME/ACNET readout of 1-turn sum
- ()=reg_DDZBIS : lpm_ff(.clock=adclkby2, .enable=NUMI_BB2,
- .data[] = NUMI_accI.result[]) with (LPM_WIDTH=26) returns(.q[0]);

- Output : the integrated bunch intensity measurement

**Works fine with one batch**
**First implementation of the damper for NuMI**

## Transverse  change with the damper working on the beam 

**Vertical and horizontal trans. ******** are measured using flying wires**

**Transverse ******** is measured right after the beam injection into the MI at 8 GeV**
**Compare transverse ******** for nominal and mis-steered injections**

**With normal injection error**
**Values of ******** : **
**10.93 ********mm-mrad  (V)  10.85 ********mm-mrad (H)**

## Observed transverse bunch oscillation using the damper system with the mis-steered injection 

- Observed transverse bunch oscillation using the damper system with the mis-steered injection
-  : big oscillations for many turns

- Horizontal

- Vertical

## Oscillation of mis-steered beam with the damper on

-   : the beam is damped down very quickly

## Measured trans. with the damper on when beam is mis-steered

- Measured trans. with the damper on when beam is mis-steered

- Value of trans.  with damper on
-  **Normal injection     : avg. 9.88 ********mm-mrad (V) & 9.28 ********mm-mrad (H)**
**           ********damper off  : avg. 10.93 ********mm-mrad (V) & 10.85 ********mm-mrad (H)**
-  **Big injection error : avg. 10.07 ********mm-mrad (V) & 8.96 ********mm-mrad (H)  **
**          ******** ****damper off : avg.  12.0 ********mm-mrad (V) & 16.21 ********mm-mrad (H)**** **

## Beam intensity without the damper: life time of the beam at 8 GeV is not excellent: 6 batches

- With the damper on at very high beam intensity  ( 3.3e13)  with improved lifetime at 8 GeV

- Beam intensity

- Beam momentum

## Reduction of beam instability using the damper for multi-batches

- Horizontal (x) and vertical (y) beam oscillations with the damper on as function of turn number (time) : 6 batches with the nominal beam injection in MI  (plots from Dennis Nicklaus)

## The damper is turned off around 50 turns: instability of the beam position grows rapidly.  The rate of instability growth in vertical direction is steeper than that in horizontal direction

- The damper is turned off around 50 turns: instability of the beam position grows rapidly.  The rate of instability growth in vertical direction is steeper than that in horizontal direction

- Horizontal

- vertical

## Current kicker (from RF cavity) for longitudinal damper does not work : too weak (?)During the shutdown 3 broadband RF cavities were installed: kick voltage will be ±1.8kV instead of  ±600V

- The status of the longitudinal damper

## Installed broadband RF cavities for damper

- MI 60 : 3 RF cavities installed last week

## Conclusion & plan

-   Significant trans.  reduction at injection is observed with the damper on
-       :  transverse damper works well
-   A high beam intensity is achieved with transverse damper operating
-   RF cavities for longitudinal damper were installed
-   New board for the damper system will be installed
-   Thorough study of the FPGA codes is needed to implement features for NuMI

## 212 MHz Sampling of Stripline Signal

***Filter Spreads signal +/-5ns in time so it will not be missed by ADC***

***Signal difference from points (A-B) has no first-order sensitivty to phase errors***