Magnet Power Supply System

T. Kawamoto
T. Sueno
N. Tokuda
T. Oki17th KEKB Accelerator Review Committee

Contents-

Existing KEKB power supplies.

-New power supplies to be developed for SuperKEKB.

-R&D and the preliminary test results.

Existing KEKB Power supplies
We have ~ 2300 power supplies:Class# of power supplies

Typical load

Small-class1885
Steering magnet etc(< 10 A, 0.5 kW)
To be reused
after appropriate maintenance and overhaul : in progress.
Medium-class
368Local Quads(< 500 A, 100 kW)
To be reused.
Large-class
14
Quad families(< 500CurrentA, 500 settingkW) resolution will be improved by 20-bit DAC.
Megawatt-class
Rubbished and replaced by 6newly developed
PSs: inprogress.
BendingandWigglers(< 1250 A, 1 MW)
Typical spec.
Stability< 20 ppm / dayRipple< 10 ppm

Setting resolution< ± 50 ppm (16-bit DAC)

First new megawatt-class power supply

Just delivered to KEK in last week
(B2E, 2012/Feb./15th @D2)
Other 9 power supplies for bending and wigglers
will be delivered by end of March.

New Power supplies to be developed for SuperKEKB*:developed in FY2011;†: in FY2012;():spec./# has not been fixed.

Power# of power supplies

Typical load

0.95 MW2*

LER / HER Bends.

0.4~1 MW

8* / 1†

LER / HER Wiggs.

< 100 kW(~ 50)

Local Q~ 10 kW (1000 A)(~ 10)QCS main~ 0.5 kW (± 50 A)(~ 50)

QCS correction< 70 kW

23*

Damping Ring (Q, B …)

< 630 kW2†

Damping Ring (Bends.)< 36 kW(Many)

Damping Ring (Others)

Target spec. of power supply for Bends and Wiggs.
Stability< 2 ppm / dayRipple< 1 ppm

Setting resolution< ± 0.1 ppm (~23-bit)

R&D 1: higher current-setting resolution
For more precise setting of the current,
increasing the DAC bits from present 16 to 20 or more is necessary.
Step 1. Try new commercial use 20-bit DAC.
(AD5791: released in 2010/March/11th by Analog Devices)
Step 2. Two 20-bit DAC’s are combined for 24-bit resolution.
Setting value
in 20-bit (major)
Setting valuein 4-bit (minor)

1/220+

DAC++
1/24

1/24

DAC

Step 3. For 24-bit resolution, another scheme has been tried:
summing the output of sixteen (= 24) 20-bit DAC’s.

Preliminary test result: two 20-bit DAC's 24-bit system
Increasing DAC input digital value by 1 least significant bit (LSB),DAC output voltage is measured by DMM KEITHLEY 2002.
(range: 2 V, integrate time in Power Line Cycles (PLC): 50, 10 moving digital filter)

DAC output voltage (µV)

+20−2−42 µV−6−80123Time (s)41 LSB (0.6 µV) response can be seen.

5×1000

R&D 2: current-stability improvement
Digital feed back control for long-term stability improvement.
+Setting valuein 20-bit (major)DAC-

1/24+

Setting valuein 4-bit (minor)+-DAC

Error Detection
DMMDCCTNP
Output terminal+

current loop-

minorvoltage loop+-Preliminary test result: digital feedback system
Long-term stability test was performed by using
a medium-class power supply (15 V, 500 A).
measured by DMM (20 V range, 10 PLC, 10 moving Filt)

0.2 ppm (2 µV/10 V)

1.4 ppm / 8 hrs(peak-to-peak fluctuation included)
8 hrs

2 ppm (20 µV/10 V)

8 hrs

7.5 ppm / 8 hrs

Summary-Small/medium-class power supplies:
Overhaul is in progress.

-Large-class power supplies for the Quad families:
Improvement is planned for more precise setting resolution,increasing the DAC bits from present 16 (LER)/18 (HER) to 20.
And overhaul is planned.

-Megawatt-class power supplies:
Old PSs were rubbished,and have been replaced by newly developed PSs: in progress.

-

New 10 megawatt-class power supplies for the main ring and23 medium-class power supplies for the damping ring
are to be delivered by end of March 2011.

-R&D has been performed, and the preliminary results are satisfactory.
24-bit setting resolution and digital feedback systemhave been applied to the new 10 megawatt-class power supplies.

Back-up slideWhy sixteen DAC's 24-bit system?
Care must be taken to the monotonicity of two DAC’s 24-bit system

Not so badBad

Non linearity and monotonicity

LSB: least significant bit
DNL: differential non linearity
INL: integral non linearity

Lose monotonicity

AD7846K (16-bit): DNL ±0.5 LSB max
INL ±2 LSB
AD5791B (20-bit): DNL ±0.75 LSB typ. (test result: <±0.1 LSB）INL ±0.5 LSB typ. (test result: -0.2～+0.6 LSB）

Typical long-term stability
Prototype power supply for QCS main coilPower supply: Transistor-dropper type (1000 A-30 V).
Test Load: 1.2 mΩ resistor
15℃‐

Temp: 20 〜27.5 ℃

25℃‐

Initial drift
9 ppm

Stability: 11 ppm / 24 hrs.

24 hrs.

How much jitter on the measured current
For precious control, lower jitter is necessary on the current monitoring.
Current is measured by a DCCT and a DMM.

Fluctuation (σ) of DCCToutput during 5min (µV)

Power supply: Transistor-dropper type (1000 A-30 V).
DCCT: 1000 A / 10 V output
DMM: KEITHLEY 2002 (10 PLC, 20 V range)
1010 µV corresponds to 1 ppm

8642

Noise level: 0.6 µV

00200

400 600 800
Current (A)1000

Typical ripple
QF4E magnet system
Power supply: Transistor-dropper type (500 A-380 V).
Load: 40 Quads connected in series around KEKB ring.
Measured voltage ripple

Measured load impedance

50 Hz 300Hz

Z ~ 0.66 Ω + 0.58 H ( f < 1kH)
50 Hz: 0.7 ppm
300Hz: 0.3 ppm

Schedule
FY2010 (H22)FY2011 (H23)FY2012 (H24)

FY2013 (H25)

FY2014 (H26)

FY2015 (H27)

4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3

R&D
Higher bits
Digital feedback
Precious monitoring

Power supply
QCS prototype

install

Load test

B (H/L), Wig (L)Design and development

Q, Sx (L/H), Wig (H)Design and development

QCS collector

Design and development

QCS main

Test with load is strongly depends on the progress ofcooling water, vaccum, control, magnet and cable installation

Install

Load tests and tuning

Design and development

Damping ring

Design and development

Steering etc

MaintenanceCovering PSs with dehumidifierParts replacement

Medium class and Small class PS (IPM, capacitor, ...)

Facility
Buildings for power supplies

DesignConstruction

Electric transformer substation
Cables (ID, removal, buy, install)
Re-arrengement of PSs

Reinforce Oho substation
buy cables

buy cables(buy cables)

Reinforce Nikko substation
Install cables and cooling pipes, system check