# Presentation: 548549

## Two Devices for HINS*

***Two Devices for HINS****
***Robyn Madrak***
*** ******Accelerator Physics Center (APC)***

- Part I: Fast
- Chopper

- Part II: Vector
- Modulators

## HINS - Purpose

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

*** ******60 MeV Linac under construction at Fermilab’s meson building***
*** ******R&D Linac which will demonstrate novel technologies used for the first time***
*** ******Technical feasibility proof of (front end) for                   ***
***  ******8 GeV Linac, Project X, etc.***

- High intensity proton source for neutrino physics/
- muon storage ring experiments

## Unique Aspects/Challenges

*** ******Solenoidal focusing ************ cleaner, axisymmetric beam***
*** ******Use of SC spoke resonators***
*** ******Fast ferrite phase shifters ***
*** ******will allow multiple cavities (and RFQ) to be driven by a single 2.5 MW, 325 MHz klystron => cost savings***
*** ******Fast Beam Chopper***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Parameters

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

***Parameters***

- * full un-chopped 3 msec pulse at klystron-limited 20 mA

## FNAL HINS

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## HINS Chopper – Part I

** *****Should the HINS be extended to an 8 GeV Linac, output beam would be  transferred to Fermilab’s Main Injector, with 53 MHz RF frequency***
*** ******HINS Linac Bunches are spaced by ******325 MHz****** (******3.1ns******)***
*** ******In MI, RF frequency is ~******53 MHz****** ******(~19ns******)***
*** ******Don’t want bunches in the 53 MHz separatrix***
********* ******Chop out ~1 of every 6 bunches***
*** ******Additional complication: 325 ≠ n ******G****** 53***
********* ******Sometimes chop 1, sometimes 2***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Traveling Wave Chopper Structure

***Traveling Wave Chopper Structure***

-  *beam is deflected by traveling pulse (electric field)*
* ****(beam)=0.073 => must slow down pulse*
*Use traveling wave “meander” structure:*
* **50 cm long*
* **16 mm between chopper plates*
* **2.4 kV per plate *
* **deflection of 6mm at end of plates*

*6 mm*

*.015 **′′*

*100*Ω

*20 mm*

*1⁄8**′′ **thick substrate (**** = 9.6)*

******=0.073**

******=0.073**

- d = 16mm

**V = +2.4 kV**

**V = -2.4 kV**

**~6ns**

******=0.073**

- chopper plates
- (meanders)

**deflection ********= 24mRad**

**Pwid < 6 ns**

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Chopper in MEBT

***length of chopper plates:  50 cm***
***drift space downstream:   30 cm***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Deflection

***length of chopper plates:  50 cm***
***drift space downstream:   30 cm***
***plate separation:               16 mm***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## We need

Two pulsers to drive the ~50 Ω meanders: +/- 2.4 kV
Max ~5.5 ns pulse width (including rise and fall time)
53 MHz rep rate
burst of 3ms @2.5Hz, or 1ms@10Hz
Programmable pulse width 
   (may sometimes chop 1 bunch, sometimes two)

→ Specs do not lead to an “obvious” solution

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

- We need
*Two pulsers to drive the ~50 **Ω** **meanders: **+/- 2.4 kV*
*Max **~5.5 ns** pulse width (including rise and fall time)*
*53 MHz rep rate*
*burst of **3ms @2.5Hz**, or **1ms@10Hz*
*Programmable pulse width *
*   **(may sometimes chop 1 bunch, sometimes two)*
*→ ****Specs do not lead to an “obvious” solution***

## Similar Choppers

***Similar Choppers***

***CERN-SPL***

***LANL-SNS***

|   | CERN-SPL | LANL-SNS | RAL/ESS | FNAL HINS |
| --- | --- | --- | --- | --- |
| Beam Energy | 3 MeV | 2.5 MeV | 2.5 MeV | 2.5 MeV |
| Electrode Length | 2 X 40 cm | 35 cm | 34 cm | 50 cm |
| Electrode Gap | 20 mm | 18 mm | 14 mm | 16 mm |
| Deflection Angle | 5.3 mRad | 18 mRad | 16 mRad | 24 mRad |
| Electrode Voltage | ±0.5 kV | ±2.35 kV | ±2.2kV | ±2.4kV |
| Pulse Rise Time | < 2ns | 10 ns | 2 ns | < 2ns |
| Pulse Duration | min 8ns | 300 ns | 12 ns | < 5.5 ns |
| Pulse Rep Rate | 44MHz | 1 MHz | 2.4 MHz | 53 MHz |
| Bunch Frequency | 352 MHz | 402.5 MHz | 280 MHz | 325 MHz |
| Burst Duration | 0.6 ms | 945 ns | 1.5 ms | 3ms, 1ms |
| Burst Rep Rate | 50 Hz | 60 Hz | 25 Hz | 2.5, 10 Hz |
| Chop Description | 3/8 bunches | On 300,off 645 ns |  | 1 or 2/6 bunches |

## Combining lower voltage pulses?

***Combining lower voltage pulses?***

- scope:
- sees 1⁄4 of ~120V signal
- (25Ω/100Ω)

- Fet A
- (~60V)

- Fet B
- (~60V)

- 75Ω

- 50Ω

- 100Ω

- ferrite

- 50Ω

- t_rise =1.4 ns
- t_fall = 2.2ns
- width = 4.1ns

- 2.5ns/div

- repeat for 10ms

- Basic Concept:
- Two 60V→50Ω pulses
- Combined to
- One 120 V→100Ω pulse

- scope

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

##  Kentech 500V Pulser

- pulse
- control cards

- PSU

- pulse
- cards

- trigger and power dist cards

- output

*before fully assembled:*

*one side of combiner:*

- five 25Ω semirigid cable
- in parallel, with ferrite

-  25Ω semirigid cable

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## 500V Pulser Output 

*~520 V pulse*

*         **5.5 ns*

*1 ms of pulses*
*@ 53 MHz*

*3 ms of pulses*
*@ 53 MHz*

***500V Pulser Output ***

*(repeats @ 10Hz)*

*(repeats @ 2.5Hz)*

- June ‘06

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## 1.2 kV Pulser

- Pulser output
- 200V/div
-  5ns/div

- 3ms burst
- 200V/div
-  400s/div

***1.2 kV ******Pulser***

- Nov ‘07

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Kentech Pulsers

*500 V Pulser was a success*
*Subsequent **1.2 kV **pulser was a success*
*Plan: **two (1.2kV**→50**Ω**)** **into **one **(2.4kV**→100**Ω**)** **output*
*This requires a **combiner** and a **meander with **100**Ω** impedance*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Microstrips in General

***Microstrips in General***

- phase velocity and impedance are
- determined by **effective dielectric constant:**

*Delay time (****) and Z**0** may be adjusted by*
* **Adjusting d, W, and also meander pathlength*
* **Using only one trace or two in parallel*
* **Adding an air gap beneath the dielectric (changes ****e**); can be used to tune ***

- view from end

- view from top

## FNAL Fabricated Meanders

- We have pursued the following:
*Use double meander design with air gap between meander and ground plane            (**50**Ω** **w/no gap, 100**Ω**/w gap)*
*Using single meander*
*Material: Rogers TMM10i, Cu clad;                    ****=9.8,        18’’ long (46 cm)            *
*Meander is formed by *
*          **routing out traces*

*double meander*

*single meander*

*single meander*

*20mm*

*40mm*

*78 mm*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Chopper Meanders

- Important Aspects
*Material: Outgassing**	**?*
*Impedance (avoid reflections)*
*Delay time (match beam ****)*
*Pulse Behavior along length (dispersion)*
*Coverage Factor*

*20mm*

*40mm*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Meander Substrate

* **Meander traces are generated by routing out traces on Rogers TMM10i, Cu clad*
* **Cheaper, faster than paste/firing/electrochemical deposition*
* **Test indicates acceptable vacuum properties*

- Terry Anderson

- @55C 8E-08 torr
- 0.63 L/s
- (with1⁄3 final surface area)

- bakeout
-  begins

- nitrogen
- backfill

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Double Meander, Impedance

***Double Meander, Impedance***

*Impedance measurements from 1 – 500 MHz*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Double Meander, Delay

***Double Meander, Delay***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

| spacing | t delay (ns) |  |
| --- | --- | --- |
| 0.062’’ | 18.8 | 0.081 |
| 0.040’’ | 21.2 | 0.072 |
| 0 | 32.3 | 0.047 |

* **Want **** = 0.073 to match beam speed*
* **Measure pulse delay in meander:*
* **Varying distance between meander and ground plane shows sensitivity *

- input pulse

- output; delayed

## Single Meanders: Impedance and Delay

***Single Meanders: Impedance and Delay***

_*Meander 1*_*: 95* Ω @~100 MHz

_*Meander 2*_*: 100.5* Ω @~325 MHz

*input pulse*

*nominal*

*0.010**′′shims *

*t delay=20.8ns*

*t delay=20.24ns*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Dispersion

***Dispersion***

*input pulse   *
*beginning*
*half way*
*     **end*

*single meander 2*

* **single meander 1*
*“**low dispersion”*

*input pulse   *
*beginning*
*half way*
*     **end*

*double meander*

-  Meanders are 18′′ long
-  Look at pulse behavior along length using high f scope probe

- 2 ns/div

- 2 ns/div

- 2 ns/div

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Coverage Factor

* **The electric field between the chopper plates is less than that for a structure in which the entire surface is conducting*
* **This must be accounted for in the chopper design when determining the voltage needed for the desired kick*

*conductor*

*dielectric*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Coverage Factor Measurements

***Coverage Factor Measurements***

*High frequency probe*
*Tip is at top ground plane*

*xy stage for position dependent measurements*

*meander*

*Ground;*
*top ground plane*
*at beam height above*
*meander*

*network analyzer*
*port 1*

*network analyzer*
*port 2*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Coverage Factor Normalization

*@ end*

*@end*

***Coverage Factor Normalization***

*Normalize to stripline with wide trace *
* **Use geometry for 50**Ω**  –  **convenient*
* **For striplines                                       **	*
*Z = 120******2****/8(ln2 + ****w/4h)**
*Use w = 25mm, 2h = 16mm*
** **R. Collin, Foundations of Microwave Engineering*

***Probe pickup signal (S******21******), 50 – 150 MHz***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## All Measured Coverage Factors

| type | Double 50Ω | Double 100Ω
 | Single 1
(low dispersion) | Single 2 
(high coverage) |
| --- | --- | --- | --- | --- |
| Coverage factor | 71% | 87% | 48% | 74% |

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Position Dependence

***Position Dependence***

- beam RMS size

- 100%

- x

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

- 20mm = 0.79′′

## Combiner

**3 ms pulse**

**combined output**

**input**

***50******Ω****** cable***

***V******1******→50******Ω***

***V******1******→50******Ω***

***50******Ω****** cable***

-  *MN60 ferrite: three 11’’ OD, 4.5’’ ID, 1’’ thick cores*
* **58 turns of  1⁄4**′′ **“superflex” cable*

***ferrite***

**1 ms pulse**

*Expect behavior to be better than this:*
* **currently we have extra unneeded cable length*
* **matching resistors (100**Ω** **to scope 50**Ω**) add extra inductance*

***Combiner***

***2V******1******→100******Ω***

***Test combiner by splitting and recombining (using our 500V pulser):***
***V******out ******= 95% V******in***

- scope

## Combiner Optimized

**input**

***ferrite***

- 46 turns of 3⁄8′′ superflex around five 1′′ MN60 cores

- 1700 V →100 Ω

- 1200 V pulse → 50 Ω

- 500 V pulse → 50 Ω

- combiner

- 100 Ω
- meander
- structure

- Kanthal 100 Ω

- High f probe, 3⁄8′′ away

***Combiner Optimized***

- 200 s/div
- 1ms pulse

- 5ns/div, 1600 V

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Heating in Meander

| Equilibrium
Temperature | 1ms, 10 Hz, 50A | 1ms, 10Hz, 41 A | 3ms, 2 Hz, 50 A |
| --- | --- | --- | --- |
| T (near trace) | 83 C | 58 C | 44C |
| T (on trace) |  |  | 65C |

- Current in meander will be 2.4 kV/100 Ω = 24 A
- Need to test heat/current handling capacity
- Use 1ms/3ms pulses:  (24A)2  x  1⁄3  x  5.3 = I2test   Itest = 32 A

- actual
- pulsed
- current

- chopping
- DF

- Skin
- depth
- factor

*Fuses @ 180A, 3ms pulse*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Chopper: Summary

***We have built prototypes for the necessary components for the chopper: the pulser, meander structures, and combiner***
*** ******The prototype pulsers from Kentech performed to specs;       ***
***For a complete chopper system we need 3 more***
*** ******We have built a combiner suited for combining these fast pulses***
*** ******We have explored different layouts for the chopper plates (meander structures). The higher coverage factor single meander is the best candidate.***
*** ******For more details, see proceedings of Linac’08 : ***
-       R. Madrak et al., “A Fast Chopper for the Fermilab High Intensity Neutrino Source (HINS)”

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Aside: Application of Chopper R&D

***to the current accelerator***

-   Initially explored the option of using a few fast, 1 kV FETs from DEI for
- Chopper pulser
-   Realized these could be used for notching in the 750 keV line:
-                **create a notch for booster kicker rise time**
- (minimize losses)
-  This effort was begun initially in collaboration with Doug Moehs
- (first attempt was chopping in the source)

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Combining three DEI FETs

*from DEI/IXYS RF*

- Use the same scheme as HINS pulser,
- combining three ~1kV → 16.7 Ω signals
- (x 30 = 50 Ω)
* **~40ns pulses 2.2****s spacing*
* **Burst of 15 pulses, repeat at 15 Hz*
* **Two pulsers: **±1.9kV*

- 1.9 kV,
- ~40 ns wide pulse
- (on test bench w/60 dB atten)

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Notching Plates in 750 keV line (H-)

- Plates: 0.9′′
- spacing

- W1

***Notching Plates in 750 keV line (H******-******)***

## Notching Study

- In Linac after tank 2
- Vplates = 2.9 kV

- ~100 ns wide notch

- 50 ns/div

- 20 ns/div

- In Linac after tank 2
- Vplates = 3.8 kV

- ~100 ns wide notch
- In booster

- ~40 ns wide notch
- In booster

***Notching Study***

- ~40 ns wide notch

- B. Pellico, R. Tomlin

- B. Pellico, R. Tomlin

- 400 ns/div

- 40 ns/div

## Part II – Vector Modulators

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

***Part II – Vector Modulators***

## HINS 325 MHz RF

***HINS 325 MHz RF***

- Pulse Transformer& Oil Tank

- IGBT Switch & Bouncer

- CAP
- BANK

- 10 kV

- 110 kV

- Charging
- Supply
- 300kW

**MODULATOR**

**325 MHz**
**2.5 MW**
**1ms@10Hz**
**or**
**4ms@2.5 Hz**

- WR2300 Distribution Waveguide

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**Fast Ferrite **
**Vector**
**Modulators**

**RF**
** ****Couplers**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**500kW**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**I**
**Q**
**M**

**10kV**

**50 kW**

**circulator**

- M

- E

- B

- T

- R F Q

- S

- S

- R

- S

- S

- R

- S

- S

- R

- S

- S

- R

**H-**

- Medium Energy
- Beam Transport
- Copper Cavities

**Radio Frequency**
**Quadrupole**

**Cryomodule #1**

**Cryomodule #2**

**TOSHIBA E3740A **

***independent phase and amplitude control in each cavity***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## How it Works

***How it Works***

**In a coaxial line filled with some dielectric (******
**v = c/****√******
**We vary ******** and thus v and phase by varying **
**H applied to the ferrite.**

*H*

- I

**ferrite**

**outer**
**conductor**

**inner**
**conductor**

**slot**
** ****in outer **
**conductor**

**supplied by **
**solenoid**

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Operates in full reflection mode (end is shorted)

Use solenoid along with shifters: phase of reflected wave determined by  of ferrite ( depends upon applied H Field)

Ferrite is Al doped Yttrium Iron Garnet (YIG) – TCI Ceramics AL-400

Required rate: 1o/s

Power Rating: ~50kW (Room Temp Cavities) 
     or ~500kW (RFQ) 

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

***Operates in full reflection mode (end is shorted)***
***Use solenoid along with shifters: phase of reflected wave determined by ************ of ferrite (************ depends upon applied H Field)***
***Ferrite is Al doped Yttrium Iron Garnet (YIG)*** – ***TCI Ceramics AL-400***
***Required rate: 1******o/************s***
***Power Rating: ~50kW (Room Temp Cavities) ***
***     ******or ~500kW (RFQ) ***

***Fermilab’s Ferrite Phase Shifter***

## Vector  Modulator:

***Modulates phase and amplitude independently:***
****
**With ******** = (********2  *****- *********3****)/2**
****** ****= (********2  *****+ *********3****)/2**

***90 Degree***
***Quad Hybrid***

**Input**
**(split between ports 2 and 3) **

***Output ******←***
***(Cavity*****)**

******2**

******3**

**circulator**

***Vector  Modulator:***

***Output power ~ *****cos****2****(*********)***
***Phase shift ~ *******

***Phase ***
***Shifters***

***shorted***
***end***

***solenoid***

***flux return***

***slot***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Two Phase Shifter Types

***For Cavities (~75 kW):***
***1******.5************ OD X 0.65************ ID X 5************ long garnet***

***For RFQ (~500 kW):***
***3************ OD X 0.65************ ID X 5************ long garnet***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Shifter Design Details

-  Center conductor: shrink fit during assembly
-  Use quarter wave matching section
- (for 50Ω)
-  Outer conductor has 0.020′′ slot (length = 9′′) to reduce eddy currents
- (gives faster response)

- solenoid
- (12 awg wire around G10)

- flux return

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Other VM Parts

- hybrid for 15⁄8 vm: Dielectric

- circulator for 15⁄8 vm:
- Ferrit-Quasar

- circulator load:
- 5kw CW
-  water cooled
- Altronics

- 6 ′′hybrid for RFQ vm: MCI
- Filled with SF6 to prevent sparking

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Phase vs. Applied Field

***useful phase shift range ~120 deg. (loss < -0.2 dB)***

- Gyromagnetic resonance
- (lossy)
- @ 2.8 MHz/Oe

***Phase vs. Applied Field***

- 325 MHz
- Low Power meas:

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Small Signal Frequency Response

***Small Signal Frequency Response***

- Open loop bandwidth: 15 kHz
***> 35 kHz w/feedback***

- Response
- (mixer)

- solenoid I
- _Program, 10 kHz_

- 0.1 ms

- 30 deg.

## Slew Rate

- Phase Shifter Slew Rate:
- (above resonance)
- 6 deg/s
- Current risetime limited by supply output, solenoid inductance
- Fast 300A power supply thanks to
- Brad Claypool, Steve Hays, Howie Pfeffer

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Beam Loading - Simulation

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

***Beam Loading - Simulation***

- Cavity 6
- Starting and stopping the compensation 4 usec prior to beam arrival time
- Beam current 26 mA
- phiS = -45 deg

- Results courtesy
- Julien Branlard

## Meson Building Test Facilities

***Meson Building Test Facilities***

**325 MHz**
**RF Test Cage**

- Please do not
- feed the animals

**2.5 MW klystron**

**First room temperature cavity**

**vector**
**modulator**

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Meson Building Test Facilities

***Meson Building Test Facilities***

- Testing the RFQ vector modulator

- Testing the 15⁄8′′ vector modulator

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Power Capabilities

***phase ~ (*************  *****+ *************)/2**

*here, both shifters’ solenoids driven by one power supply*
********** ****=***** ***************

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Power Capabilities

***Power Capabilities***

*** ******15⁄8 VM for cavities******: ***
-  good to >75 kW
-  Shifters alone could be used in a 200 kW VM if used with oil in ferrite part of coax line
- (higher power quad hybrid & circulator would be needed)

***RFQ VM***
-  Shifters and Hybrid filled with SF6: Good to > 500 kW
-  Current hybrid is 6′′
-  Stripline “500 kW” Circulator failed: Getting a new one from Ferrite

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Vector Modulators: Summary

*** ******The 15⁄8******′′ vector modulators can operate well up to 75 kW (more than needed for the RT cavities)***
*** ******The RFQ vector modulator elements:***
*** ****phase shifters good to ~600 kW*
* **hybrid good to ~600 kW*
* **initial circulator failed; new Ferrite**TM** model on order*
***The speed of the response for the cavity shifters is 6X as fast as the original spec***
* **bandwidth > 35 kHz for a first attempt at feedback*
*** ******For more details, see proceedings of Linac’08 : ***
-       R. Madrak and D. Wildman, “High Power 325 MHz Vector Modulators for the Fermilab High Intensity Neutrino Source (HINS)”
***  ***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Conclusions

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

***Conclusions***

-  ***HINS is a key part of Fermilab’s Accelerator R&D program, and likely a key part of its future physics program***
*** ******We have demonstrated the workability of two of its more challenging components***

## Backup Slides

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Kentech 500V Prototype Pulser Scheme

***Kentech 500V Prototype Pulser Scheme***

*10 pulse cards: 50V**→5**Ω*

*5 FETS/card (in parallel)*
*each FET drives 25*Ω

*center conductor*

*outer conductor*

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***5******Ω***

***25******Ω***

***25******Ω***

*pulse control cards*

*output: 500V**→50**Ω*

*25*Ω *semirigid cable*
* **with ferrite*

*five 25*Ω *semirigid cable*
*in parallel, with ferrite*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Coverage Factor, Meanders

*single meander signal to 500 MHz*

*double meander (100**Ω**)around 100 MHz*

*single meander (100**Ω**) **around 100 MHz*

*Which gives*:*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

| type | c |
| --- | --- |
| double | 87% |
| Single 1 | 48% |

**Relative to normalization measurement;*
*After correcting for impedance difference and reflected power*

## Heating in Meander

- Final Pulse: 2.4 kV→Z= 100Ω, 1ms@10Hz or 3ms@2.5Hz, Chop ≤ 30%
- Meander Traces: 70m thick, R(DC) = 2.7 Ω

- - Or -

-  Measure power spectrum of pulses; normalize to (2.4kV)2/100 Ω x 1⁄3 x 0.01 = 192W
-  Convolute with S21 thru meander; this give Pdiss = 46 W
-  I2test x  DFtest x 2.7 Ω = 46W   Itest = 41 A

- actual
- pulsed
- power

- chopping
- DF

- DF

- 1ms @ 10Hz

-   With safety factor, test at 50 A

- low power, spectrum analyzer

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Notching Study

- +1.9 kV

- -1.9 kV

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Using one or two single power switches:

*from DEI/IXYS RF*

- min width pulses @20MHz:

- 20ns/div

- 1ms/div

- → *cannot get to a narrow enough pulse ...*

*With two switches:*
*Pulses are narrower, but*
*Still not narrow enough*

- 4ns/div

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## Using one or two single power switches:

***Using one or two single power switches:***

-  The DEI FETS *can* be used to make a very narrow pulse by charging cable in the drain
-  But in this case we cannot attain the desired 53 MHz rep rate

- 20ns/div

- 4ns/div

*With a slightly lower current version of the switch:*

- Robyn Madrak - FNAL APT Seminar - 12/16/2008

## DEI FETS for H− Source

**Doug Moehs**

- 20 pulses

- single pulses

* **DEI FETS were useful for beam notching in **H**−* *source for the current linac*
* **~40ns pulses 2.2****s spacing*
* **Burst of 15 pulses, repeat at 15 Hz*
* **Two pulsers: **±800V*

- toroid response shows notched beam

**trigger signal (time offset)**

***DEI FETS for H******−****** Source***

- Robyn Madrak - FNAL APT Seminar - 12/16/2008