# Presentation: 014188

## Status of the LAPPLHC AC Dipole Task

**Ryoichi Miyamoto**
**University of Texas at Austin**
**2/27/2008 FNAL LARP Meeting**

_**Collaborators**_
**BNL: M. Bai, R. Calaga, W. Fischer, P. Oddo**
**FNAL: A. Jansson, M. Syphers**
**UT Austin: S. Kopp, R. Miyamoto**
**CERN: J. Serrano, H. Schmickler **

## Overview of FY08

**System development**
- Circuit design (CERN).
- Test to stack multiple (Crown or Labgrupen) audio amplifiers (FNAL, CERN).
- Work on tunability of the resonant circuit (maybe as an upgrad) (BNL).
**Further development of measurement schemes**
- On-line applications for linear optics measurements (BNL).
- Test linear and nonlinear optics measurements (FNAL).
**After FY08**
- The task completes this year?
- Hire a postdoc to work on on-line applications? (NSF approved the proposal but fonds are up in air).
- TBT analysis (or even optics measurement) task?

## Tevatron AC Dipole System

**7.5 ****μ****F**

**Magnet + Cable:**
**8***** *****μ****H & 90 m****Ω**

**8 ****μ****F**

**Transformer**
** ****Balanced ****→**** Unbalanced**
** ****Adjust impedance**

**Audio Amp**
**20***** *****kHz & 8 kW**

**+**

**−**

**|Z| ~ ****8**** ****Ω**

**±0.04 in tune**

**~1.8 mm oscillation (1 TeV)**

_**Tevatron AC Dipole System**_

## AC Dipoles for the Tevatron, RHIC,and LHC

| Machine | RHIC | Tevatron | LHC |
| --- | --- | --- | --- |
| E [GeV] | 250 | 980 | 7000 |
| σ [mm] | 0.75 | 0.5 | 0.3 |
| |νd - ν| | ≥ 0.01 | ≥ 0.01 | ≥ 0.01 |
| βarc, βacd [m] | 45, 11 | 80, 47 | 180, 260 |
| (Bl)acd for 4σ [Gm] | 140 (105) | 140 (115) | 200 |
| frev [kHz] | 78 | 48 | 11 |
| ν, 1-ν | 0.69, 0.31 | 0.58, 0.42 | 0.3, 0.7 |
| facd [kHz] | 55 | 20.5 | 3, 8, 14, 19 |

_**AC Dipoles for the Tevatron, RHIC,**__**and LHC**_

_**LHC AC dipoles will be the Tevatron style.**_

## Status of Work at CERN

- CERN has decided to adopt the FNAL solution
- 4 pingers (MKQs)
- Lab-Gruppen FP13000
- Spec: 1800 A in MKQ for 4σ @ 7 TeV
- Tests using new two amplifiers and 4:1 transformers
- 1500A current achieved (2128A should be possible).
- The 4σ (1800A) goal seems in reach.
- Peter Oddo (BNL) has been working
-     with Javier Serrano to implement
-     CERN system.

## Goal:  Tunability of Resonant Circuit (BNL)

_**Goal:  Tunability of Resonant Circuit (BNL)**_

- Peter Oddo (BNL) is developing continuous tuning technique using single switched capacitor with MOSFT at BNL
- Tunes resonant frequency by varying parallel capacitor
- C changes because of variable duty cycle of the switch
- Simulations suggest D*f ~ *400 Hz

## Intermediate Solution: Capacitor Bank

_**Intermediate Solution: Capacitor Bank**_

- Bit1

- 5-bit binary-weighted capacitor-bank
- 0.255-0.345 (±15%) tune range
- 2.867-3.880kHz
- 0.002-0.005 tune steps
- 22-54 Hz
- Static MOSFET switching
- Can be replaced with mechanical switches or straps
- Conservative design
- Can withstand CW operation
- Peter and Mei have been working with Javier Serrano this Fall to implement this solution

- Bit0

- Bit2

- Bit3

- Bit4

-  GND Plate

-  MOSFET Module

- Capacitor

-  Coil/Drive Plate

## 7.33-9.04kHz (±10%) range
Basic Topology, 0.56W,  Q=15-19
Coil current fairly constant ~2.2Apk
3rd harmonic –33dBc
Consistent with simulation

- Basic Topology, 0.56W,  Q=15-19
- Coil current fairly constant ~2.2Apk
- 3rd harmonic –33dBc
- Consistent with simulation

_**Low-power Switched-capacitor Results**_

- Always on

- Always off

- Switching

- 7.33kHz

- 9.04kHz

- 8.67kHz

- Coil current

- Coil voltage

- Drive current

- Switch voltage

## Initial Conclusions on Switched Cap’s

- Maximum Q limited by existing MOSFET technology
- MOSFETs evaluated have a dissipation factor of 0.45-1% (or Q 100-220)
- The need for many paralleled MOSFETs favor using a binary weighted capacitor-bank and modulating the LSB
- Modulating a smaller capacitance will also reduce distortion
- Modulation is not necessary for the LHC (low-Q)

## A New Linear Optics Measurement Scheme(FNLA, Submitted to PRST-AB.)

_**true **__***β***_

_***δ***__*** = -0.01***_

_***δ***__*** = -0.02***_

_**A New Linear Optics Measurement Scheme**__**(FNLA, Submitted to PRST-AB.)**_

**Driven motion ****≠ Free Betatron Motion**

## Detuning Measurement (FNAL)

|  | αy,y [mm-1 mrad-1] |
| --- | --- |
| “Estimate” | 0.0207 |
| Measurement | 0.020 |

**y [mm]**

**number of revs**

**number of revs**

**2000**

**4000**

**6000**

**8000**

**0**

**2000**

**4000**

**6000**

**8000**

**0**

**0**

**-2**

**-4**

**-6**

**2**

**4**

**6**

**8**

## Driving Term Measurements Based on the Spectrum of TBT Data (FNAL)

***ν*****d**

***ν*****d**

**2*****ν*****d**

**2*****ν*****d**

**3*****ν*****d**

**3*****ν*****d**

***ν***

***ν***

**closed orbit**

## Driving Term Measurements Based on the Spectrum of TBT Data 2 (FNAL)