GBAR experiment - Revision history

Vigen at 11:09, 7 April 2026

2026-04-07T11:09:47Z

← Older revision		Revision as of 11:09, 7 April 2026
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	[https://inspirehep.net/experiments/1108191 GBAR experiment] record on INSPIRE-HEP		[https://inspirehep.net/experiments/1108191 GBAR experiment] record on INSPIRE-HEP
	[[Category:AD experiments]]		[[Category:AD experiments]]
			[[Category:FAPlist]]

Vigen at 11:07, 7 April 2026

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← Older revision		Revision as of 11:07, 7 April 2026
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	~~{{Short description\|Experiment at the Antiproton Decelerator}}~~
	~~{{Antiproton_Decelerator}}~~
	~~[[File:CERN Antimatter factory - GBAR experiment.jpg\|thumb\|CERN Antimatter factory – GBAR (Gravitational Behaviour of Anti hydrogen at Rest) experiment\|263x263px]]~~
	'''GBAR''' ('''G'''ravitational '''B'''ehaviour of '''A'''nti hydrogen at '''R'''est), '''AD-7 experiment''', is a multinational collaboration at the [[Antiproton Decelerator]] of [[CERN]].		'''GBAR''' ('''G'''ravitational '''B'''ehaviour of '''A'''nti hydrogen at '''R'''est), '''AD-7 experiment''', is a multinational collaboration at the [[Antiproton Decelerator]] of [[CERN]].

	The GBAR project aims to measure the free-fall acceleration of ultra-cold neutral anti-hydrogen ~~[[Antihydrogen\|~~atoms]] in the terrestrial [[gravitational field]]. By measuring the free fall acceleration of anti-hydrogen and comparing it with acceleration of normal hydrogen, GBAR is testing the [[equivalence principle]] proposed by [[Albert Einstein]]. The equivalence principle says that the gravitational force on a particle is independent of its internal structure and composition.<ref>{{Cite web\|title=GBAR\|url=https://home.cern/science/experiments/gbar\|access-date=2021-06-29\|website=CERN\|language=en}}</ref>		The GBAR project aims to measure the free-fall acceleration of ultra-cold neutral anti-hydrogen atoms in the terrestrial gravitational field. By measuring the free fall acceleration of anti-hydrogen and comparing it with acceleration of normal hydrogen, GBAR is testing the equivalence principle proposed by Albert Einstein. The equivalence principle says that the gravitational force on a particle is independent of its internal structure and composition.<ref>{{Cite web\|title=GBAR\|url=https://home.cern/science/experiments/gbar\|access-date=2021-06-29\|website=CERN\|language=en}}</ref>

	== Experimental setup ==		== Experimental setup ==
	The experiment consists of preparing anti-hydrogen ~~[[ion]]s~~ (Hbar+positronium- one [[antiproton]] and two ~~[[positron]]s~~) and sympathetically cooling them with Be+ ions to less than 10 μK. The ultra-cold ions are then ~~[[Photoionization\|~~photoionized]] just above the threshold using a laser pulse; this removes the outermost positron and forms neutral anti-hydrogen. The free-fall time of these atoms over a known distance is then measured. This experimental technique is based on the idea proposed by T. Hansch and J. Walz.<ref>{{cite journal \|last1=Pérez \|first1=P. \|display-authors=etal \|year=2015 \|title=The GBAR antimatter gravity experiment \|journal=Hyperfine Interactions \|volume=233 \|issue=1–3 \|pages=21–27 \|doi=10.1007/s10751-015-1154-8\|bibcode=2015HyInt.233...21P \|s2cid=119379544 }}</ref><ref name=":0">{{Cite book\|last1=Chardin\|first1=G.\|url=https://cds.cern.ch/record/1386684/\|title=Proposal to measure the Gravitational Behaviour of Antihydrogen at Rest\|last2=Grandemange\|first2=P.\|last3=Lunney\|first3=D.\|last4=Manea\|first4=V.\|last5=Badertscher\|first5=A.\|last6=Crivelli\|first6=P.\|last7=Curioni\|first7=A.\|last8=Marchionni\|first8=A.\|last9=Rossi\|first9=B.\|date=2011\|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC}}</ref>		The experiment consists of preparing anti-hydrogen ions (Hbar+positronium- one antiproton and two positrons) and sympathetically cooling them with Be+ ions to less than 10 μK. The ultra-cold ions are then photoionized just above the threshold using a laser pulse; this removes the outermost positron and forms neutral anti-hydrogen. The free-fall time of these atoms over a known distance is then measured. This experimental technique is based on the idea proposed by T. Hansch and J. Walz.<ref>{{cite journal \|last1=Pérez \|first1=P. \|display-authors=etal \|year=2015 \|title=The GBAR antimatter gravity experiment \|journal=Hyperfine Interactions \|volume=233 \|issue=1–3 \|pages=21–27 \|doi=10.1007/s10751-015-1154-8\|bibcode=2015HyInt.233...21P \|s2cid=119379544 }}</ref><ref name=":0">{{Cite book\|last1=Chardin\|first1=G.\|url=https://cds.cern.ch/record/1386684/\|title=Proposal to measure the Gravitational Behaviour of Antihydrogen at Rest\|last2=Grandemange\|first2=P.\|last3=Lunney\|first3=D.\|last4=Manea\|first4=V.\|last5=Badertscher\|first5=A.\|last6=Crivelli\|first6=P.\|last7=Curioni\|first7=A.\|last8=Marchionni\|first8=A.\|last9=Rossi\|first9=B.\|date=2011\|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC}}</ref>

	Along with antiprotons from AD, GBAR also needs a constant flux of positrons. For this, a small accelerator with a [[tungsten]] target is used. An electron beam of 10MeV strikes this target, and positrons are collected by using a magnetic separator to filter out ~~[[Electron\|~~electrons]] and the ~~[[Gamma ray\|~~gamma-ray]] background. These positrons are then trapped in [[Penning–Malmberg ~~trap]]s~~ and cooled down.<ref>{{Cite book\|last=Perez\|first=P.\|url=https://cds.cern.ch/record/2693263?ln=en\|title=AD-7/GBAR plans after LS2\|date=2019\|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC\|series=Memorandum}}</ref><ref name=":0" />		Along with antiprotons from AD, GBAR also needs a constant flux of positrons. For this, a small accelerator with a tungsten target is used. An electron beam of 10MeV strikes this target, and positrons are collected by using a magnetic separator to filter out electrons and the gamma-ray background. These positrons are then trapped in Penning–Malmberg traps and cooled down.<ref>{{Cite book\|last=Perez\|first=P.\|url=https://cds.cern.ch/record/2693263?ln=en\|title=AD-7/GBAR plans after LS2\|date=2019\|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC\|series=Memorandum}}</ref><ref name=":0" />

	Using a neutral particle for GBAR experiment is necessary in order to avoid any kind of [[electromagnetic interference]]. In theory, the electrically neutral ~~[[Antineutron\|~~antineutrons]] would be the smallest chunks for this experiment, but they cannot be used to due their quick decay time. The next simplest particle is therefore the antihydrogen.<ref name=":0" />		Using a neutral particle for GBAR experiment is necessary in order to avoid any kind of electromagnetic interference. In theory, the electrically neutral antineutrons would be the smallest chunks for this experiment, but they cannot be used to due their quick decay time. The next simplest particle is therefore the antihydrogen.<ref name=":0" />

	== GBAR collaboration ==		== GBAR collaboration ==
	The GBAR collaboration comprises the following institutions:~~{{columns-list\|colwidth=30em\|~~		The GBAR collaboration comprises the following institutions:
	*[[French Alternative Energies and Atomic Energy Commission~~\|CEA]]~~, France		*French Alternative Energies and Atomic Energy Commission, France
	*[[ETH Zurich]], Switzerland		*[[ETH Zurich]], Switzerland
	*[[University of Mainz]], Germany		*University of Mainz, Germany
	*[[Kastler–Brossel Laboratory]], France		*Kastler–Brossel Laboratory, France
	*CSNSM, [[Paris-Saclay University]], France		*CSNSM, Paris-Saclay University, France
	*[[RIKEN]], Japan		*RIKEN, Japan
	*[[University of Tokyo]], Japan		*University of Tokyo, Japan
	*[[University of Strasbourg]], France		*University of Strasbourg, France
	*[[Uppsala University]], Sweden		*Uppsala University, Sweden
	*[[Stockholm University]], Sweden		*Stockholm University, Sweden
	*[[Swansea University]], UK		*Swansea University, UK
	*National Centre for Nuclear Research, Poland		*National Centre for Nuclear Research, Poland
	}}

	== See also ==		== See also ==
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	== External links ==		== External links ==
	[https://inspirehep.net/experiments/1108191 GBAR experiment] record on [[INSPIRE-HEP]]		[https://inspirehep.net/experiments/1108191 GBAR experiment] record on INSPIRE-HEP
	~~[[Category:Particle experiments]]~~		[[Category:AD experiments]]
	[[Category:~~CERN~~ experiments]]

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{{Short description|Experiment at the Antiproton Decelerator}}
{{Antiproton_Decelerator}}
[[File:CERN Antimatter factory - GBAR experiment.jpg|thumb|CERN Antimatter factory – GBAR (Gravitational Behaviour of Anti hydrogen at Rest) experiment|263x263px]]
'''GBAR''' ('''G'''ravitational '''B'''ehaviour of '''A'''nti hydrogen at '''R'''est), '''AD-7 experiment''', is a multinational collaboration at the [[Antiproton Decelerator]] of [[CERN]].

The GBAR project aims to measure the free-fall acceleration of ultra-cold neutral anti-hydrogen [[Antihydrogen|atoms]] in the terrestrial [[gravitational field]]. By measuring the free fall acceleration of anti-hydrogen and comparing it with acceleration of normal hydrogen, GBAR is testing the [[equivalence principle]] proposed by [[Albert Einstein]]. The equivalence principle says that the gravitational force on a particle is independent of its internal structure and composition.<ref>{{Cite web|title=GBAR|url=https://home.cern/science/experiments/gbar|access-date=2021-06-29|website=CERN|language=en}}</ref>

== Experimental setup ==
The experiment consists of preparing anti-hydrogen [[ion]]s (Hbar+positronium- one [[antiproton]] and two [[positron]]s) and sympathetically cooling them with Be+ ions to less than 10 μK. The ultra-cold ions are then [[Photoionization|photoionized]] just above the threshold using a laser pulse; this removes the outermost positron and forms neutral anti-hydrogen. The free-fall time of these atoms over a known distance is then measured. This experimental technique is based on the idea proposed by T. Hansch and J. Walz.<ref>{{cite journal |last1=Pérez |first1=P. |display-authors=etal |year=2015 |title=The GBAR antimatter gravity experiment |journal=Hyperfine Interactions |volume=233 |issue=1–3 |pages=21–27 |doi=10.1007/s10751-015-1154-8|bibcode=2015HyInt.233...21P |s2cid=119379544 }}</ref><ref name=":0">{{Cite book|last1=Chardin|first1=G.|url=https://cds.cern.ch/record/1386684/|title=Proposal to measure the Gravitational Behaviour of Antihydrogen at Rest|last2=Grandemange|first2=P.|last3=Lunney|first3=D.|last4=Manea|first4=V.|last5=Badertscher|first5=A.|last6=Crivelli|first6=P.|last7=Curioni|first7=A.|last8=Marchionni|first8=A.|last9=Rossi|first9=B.|date=2011|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC}}</ref>

Along with antiprotons from AD, GBAR also needs a constant flux of positrons. For this, a small accelerator with a [[tungsten]] target is used. An electron beam of 10MeV strikes this target, and positrons are collected by using a magnetic separator to filter out [[Electron|electrons]] and the [[Gamma ray|gamma-ray]] background. These positrons are then trapped in [[Penning–Malmberg trap]]s and cooled down.<ref>{{Cite book|last=Perez|first=P.|url=https://cds.cern.ch/record/2693263?ln=en|title=AD-7/GBAR plans after LS2|date=2019|others=CERN. Geneva. SPS and PS Experiments Committee, SPSC|series=Memorandum}}</ref><ref name=":0" />

Using a neutral particle for GBAR experiment is necessary in order to avoid any kind of [[electromagnetic interference]]. In theory, the electrically neutral [[Antineutron|antineutrons]] would be the smallest chunks for this experiment, but they cannot be used to due their quick decay time. The next simplest particle is therefore the antihydrogen.<ref name=":0" />

== GBAR collaboration ==
The GBAR collaboration comprises the following institutions:{{columns-list|colwidth=30em|
*[[French Alternative Energies and Atomic Energy Commission|CEA]], France
*[[ETH Zurich]], Switzerland
*[[University of Mainz]], Germany
*[[Kastler–Brossel Laboratory]], France
*CSNSM, [[Paris-Saclay University]], France
*[[RIKEN]], Japan
*[[University of Tokyo]], Japan
*[[University of Strasbourg]], France
*[[Uppsala University]], Sweden
*[[Stockholm University]], Sweden
*[[Swansea University]], UK
*National Centre for Nuclear Research, Poland
}}

== See also ==

# [[Antiproton Decelerator]]
# [[AEgIS experiment]]

== References ==
{{Reflist}}

== External links ==
[https://inspirehep.net/experiments/1108191 GBAR experiment] record on [[INSPIRE-HEP]]
[[Category:Particle experiments]]
[[Category:CERN experiments]]