Krasnykh, Anatoly

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Analysis	of	Approaches	for	a	Design	of	APS‐U	Fast	Injection	SystemFor	Mini	Kicker	Work	Shop	in	ANLAnatoly	Krasnykh10/25/2013SLAC-WP-096Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES.Outline• Approaches	for	Broadband	Kicker	Structures Even	and	Odd	TEM‐modes	 Kicker	directivity Kicker	end	effects Kicker	components	(feedthrough,	electrodes,	etc.)• Analysis	for	Kicker	Drivers Thyratron	(or	Pseudo‐Spark)	based	approaches	 Shock	wave	transmission	lines	as	an	assist	of	fast	pulsers MOSFET	based	pulser	concepts DSRD	as	an	assist	for	fast	pulsersSome	additional	details	related	to	this	issue	could	be		found		in	SLAC‐WP‐077,	SLAC‐WP‐078,	SLAC‐WP	where	the	ILC	DR	fast	TEM‐mode	kicker	problems		and	other	issues	of	a	HP	nsec	technology	had	been	discussed.	TEM‐mode	Even	and	Odd	Kicker	ImpedancesPage 3• Pulsers produce	a	transvers	kick.	The	odd	TEM	mode	is	excided.• The	bunch	pusses	a	kicker	structure	without	offset.	The	even	TEM	mode	is	generated	in	the	kicker	structure.• The	field	patterns	for	modes	are	dissimilar.	As	a	result	the	impedances	are	different.• Matching	both	impedances	is	possible	by	the	introduction	of	the	ground	fenders.• Additional	fenders	will	reduce	the	beam	impedance	and	will	help	the	SR	beam	dynamics.Zodd = 50 OhmsZeven = 64 OhmsZodd = 49 OhmsZeven = 55 OhmsKicker	Electrodynamics:	Ground	Fenders	Page 4Beam Impedance Ratio for the (59.5‐1725.5) MHz range is ~1.6.This ratio is reduced for the higher frequencies (in 3.6‐5 normalized frequencyrange). Geometry of the kicker ends (geometry of paddles and absence oftapering on the electrode ends, i.e. the absence of transient region) aredependable for a reduction of Beam Impedance Ratio.TFB Kicker Beam Impedance Comparison0102030405060700 0.5 1 1.5 2 2.5 3 3.5Normalized Frequency, f0=476MHzZ||, Ohmwithout fenderswith fendersLesson	Learned	(LER	X‐TFB	TEM‐Kicker)Page 5Longitudinal Beam Impedance for TFB Kicker vs. Frequncy0501001502002503003500 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5f/f0_rfZ||, Ohm|| 34306 @3102avkavgZ OhmP W AV Vl6312||im||7.4 1010 405 5 40 102205010m avtpeakp msurfkTI i AZ OhmV Z I kVVE Ecm      The kicker ends are in charge for this freq. rangeLesson	Learned	(LER	X‐TFB	TEM‐Kicker)Page 6A	tapered	ends	are	neededA	broadband	kicker	structure	will	be	needed!	Does	mismatch	be	allowed?	Page 750 Ohms     100 Ohms    50 OhmsThere	will	be	an	impedance	mismatch	Directivity:	Kicker	End	EffectsExample is based on experimental results from PEP-IIHER, single bunch 0.8mA, 16.5 MV, att=26dB-70-60-50-40-30-20-1000 200 400 600 800 1000 1200 1400 1600 1800 2000f, MHzPb• Sigma_beam < dR (a condition) • dt_b < 2tp + tk (a root of problem)• Reflection on the (Z0, Zp, Zk) nodes (a result)• Dissipation in kicker electrodes (an effect)Z0Zk, tkZp, tpZp, tpZ0dt_bBeam induced power is in both feeders !!!HOM power to the kicker loadHOM power to the amplifierPaddles regions Page 8Loss	of	Directivity:	HOM	Simulations	(single	bunch)Decay anddisperse  Page 9Advanced	kicker	structurePage 10Sasha’sproposalSimilar	to	a	balun‐type	impedance	x‐fmrFeedthrough	Performances	Page 11      t1 t2 A A N-type7/16 inch DINBetter	feedthroughs	are	needed:	Broadband,	HV,	vacuum	tight,	bake	able,	identicalMay	a	topic	be	for	SBIR?TEM‐mode	Kicker	SystemPage 12• Kicker	housing	with	plates• Feedthroughs	with	feeders Loads Neg.	and	Pos.	pulse	generatorsSingle	charging	voltage	for	both	+	and	‐ armsIsolation	x‐fmr	is	needed(a	source	of	asymmetry)Load	(Att.)Load	(Att.)HV	Broadband	Loads	and	AttenuatorsPage 1320+kV	peak,	50	Ohm,	<	1	nsecfrom	Jon	BarthHome	Made	HV	AttenuatorsFast	Kicker	Drivers:	Thyratrons	and	Pseudo‐Spark	SwitchesPage 14High	power	handling	(50+kV,	kA)Marginal	di/dt,	dV/dt (~10E12	A/sec)Recovery	time	too	longLife	time	may	be	limited	and	operation	costly		(to	keep	the	optimal	pressure)	V.	Popov,	PAC09,	TU6RFP080Thyratron	based	approaches	may	need		in	a	shock	wave	(SW)	transmission	line	(TL)	assistance	Approach	would	be	recommended	for	an	evaluation	of	shorter	and	better	shape	pulsesCourtesy		I.	Kataev &		I.	MeshkovPage 15Potential	Fast	Kicker	Diver	Concepts1rswtH HOMLimitation	of	SW	TL	AssistantPage 16Transmission	line	with	ferromagnetic	medium	needs	a	high	current.	More	current	will	be	produced	by	a	higher	applied	voltage.High	electric	fields	may	produce	the	ionization	in	ferromagnetic	media.	Plasma	formation	and	breakdown	are	a	killer	of	shock	wave	formation.E_ferrite ~	10	kV/cm,	(for	long	life	time:	E	~	5	kV/cm	is	acting	electric	field)	 gives	the	rise/fall	times	~1	nsec52.5 10rswtHSmall	size	NiZn toroid	cores		are	preferable.	A	needed	length	of	the	oil	filled	coax	depends	on	an	initial	rise	time	and	magnetic	core	parameters.	A	design	of	SW	TL	would	require	conducting	the	R&D.	May	a	topic	be	for	SBIR?Kicker	Drivers:	MOSFET	based	ApproachesPage 17A	single	MOSFET	voltage	hold	off	is	less	than	2	kV,	switching	current	is		<100	A,	and	a	rise	time	~5	nsec	@	high	impedance	load.	DE	and	APT	are	leaders	in	the	fast	MOSFET	industry.		+_4	kV	@	50	Ohm	Loads,	~200	ea.	APT	MOSFETsA	higher	output	voltage	will	require	more	cells.	A	rise	time	will	degrade.	For	example,	DARHT‐II	kicker,	+_20	kV	@	50	Ohm	loads,	rise	time	is	~10	nsecA	nsec	switching	sub	kA	currents	will	employ	the		array	of	MOSFETsCourtesy	Ed	Cook	MOSFET	based	Approaches	(cont.)Page 18Behlke HV switches (array of stacked MOSFETs) Technical Data (for example):  0.8 x 21 kV ~17 kV @ 250A  on rise time ~40 nsecBest guess:  5 each of them (an effective impedance  is ~15 Ohm),  + SW  TLs, and TL-based x-fmr  20+kVp @15 nsecJust		buy	bunch	of	them	and	combine	the	TLs	with	TL‐based	x‐fmrs to	get	the	required	voltage	on	resistive	load.Apparently	home	made	TLs	are		will	be	needed(a	rise	time	is		realized	on	rather	high	resistive	loads)		Fast	Pulsers with	a	DSRD	AssistPage 19• A DSRD is a fast solid state device that can improve the switching performance ofindustrial high power switches ( thyratrons, MOSGETs, etc.).• All mentioned above kicker drivers are based on turn ON switches (SW relates alsoto this class). DSRD mode operation is based on a turn OFF mode. DSRD is a devicewith two electrodes (anode and cathode). A special circuit (a pumping circuit ofthe DSRD) is needed to realize the fast opening mode. The pumping circuit has toprovide a current flow through the DSRDiode in forward and reverse directions.There are several electronic circuits to create such current flow.#1 #2 #3#4Pulsers with	DSRD	Assist	(cont.)Page 20L vs. TL #4Overall	CommentsPage 21• Kicker	structure	is	an	efficient	HOM	power	extractor• Peak	HOM	voltage	and	average	power	at	the	feeder	may	be	sufficient	to	act	on	the	kicker	pulser	system	if	the	kicker	structure	has	been	designed	with	a	narrow	bandwidth• Feeder	imperfections	(real	cables,	feedthroughs,	kicker	electrodes,	loads)	are	one	source	of	residual	energy	between	bunches.	HOM	spectrum	is	broad	and	imperfections	could	select	and	capture	the	“right	mode”.	Common	actions	(HV	peak	and	HOM)	need	to	be	careful	evaluated	and	mitigated				• Best	guess:	thyratron/MOSFET	pulser	with	an	assistance	of	shock	wave	(or	DSRD	stack	as	option)	is	more	attractive	concept	for	the	APS‐U	injection	system• A	practical	evaluation	(R&D)	of	prototypes	will	be	necessary	to	allow	a	optimal	selection	of	injection	systemBackup	SlidesPage 22Rise	time	(10‐90%)	=	1.7nsPulse	width	(FWHM)	=	4.7nsCourtesy	FID	Technology	Backup	SlidesPage 23Courtesy	G.	Mesyats#2Backup	SlidesWafer # R9-16a in DO-35 packageCrystal Run time Horiz	scale,	nsec Vp	@50	Ohm,	V FWHM,	nsec Rise,	nsec Fall,	nsecR9‐16 20120127 20:29:07 0.5 304 0.914 0.826 0.422R9‐16 20120127 20:29:53 5R9‐16&R9‐16 20120127 20:42:56 1 124 2.2 0.77 0.943R9‐16&R9‐16 20120127 20:52:12 1 127 2.3 0.74 0.79

Analysis of Approaches for a Design of APS-U Fast Injection System

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Analysis of Approaches for a Design of APS-U Fast Injection System

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