Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2608.23587

Ultracold Neutron Sources: An Essentially Enhanced Optimal Operation Temperature for Ortho-Deuterium-Based Superthermal Converters

Erik Walz, C. Morkel

Published Aug 12, 2026• 0 citations
arXivHTMLPDF

Abstract

There is a longstanding dogma in the physics of ultracold neutrons (UCN): The optimal temperature of ortho-deuterium based UCN-sources must not exceed $5\,\mathrm{K}$. This value has been established by the pioneering work of Golub et al. decades ago, utilizing previously established cross sections for solid ortho-deuterium. But recently, an improved calculation of the crucial 1-phonon up-scattering cross section - using the so-called corrected Incoherent Approximation - leads to a new upper limit for the optimal operation temperature of ortho-deuterium based UCN sources. After a discussion of the relevant cross sections of the \(\mathrm{D}_2\)-molecule we conclude that the optimal temperature lies between $10\,\mathrm{K}$ and $12\,\mathrm{K}$, a factor 2 higher than estimated earlier. This offers significantly relaxed cryogenic conditions for UCN experiments with solid ortho-deuterium and especially for the operation of ortho-deuterium based ultracold neutron sources.

DOI
10.48550/arxiv.2608.23587

Related papers

NANOPARTICLES AS A POSSIBLE MODERATOR FOR AN ULTRACOLD NEUTRON SOURCE

Валерий Викторович Несвижевский, G. Pignol, Konstantin V. Protasov

Ultracold and very cold neutrons (UCN and VCN) interact strongly with nanoparticles due to the similarity of their wavelengths and nanoparticles sizes. We analyze the hypothesis that this interaction can provide efficient cooling of neutrons by ultracold nanoparticles at certain experimental conditions, thus increasing the density of UCN by many orders of magnitude. The present analytical and numerical description of the problem is limited to the model of independent nanoparticles at zero temperature. Constraints of application of this model are discussed.

arXiv:nucl-th/0510021•International Journal of Nanoscience•Dec 1, 2007•22 citations

On control of kinematic parameters of ultracold neutrons in waveguides

Лев Абрамович Ривлин

The possibility of controlling the kinematic parameters of ultracold neutrons (UCNs) is analysed by the example of a waveguide transfer and transformation of 2D images in ultracold neutrons and by the example of an increase in the concentration and deceleration/acceleration of ultracold neutrons during their transport in the waveguide with a variable cross section. The critical parameters of the problem are estimated, which indicates both consistency of the proposed approach and the emerging experimental limitations.

Quantum Electronics•Oct 15, 2010•1 citation

A new escape channel for ultracold neutrons in traps

Peter W. Geltenbort, Валерий Викторович Несвижевский, D. G. Kartashov +9 more

A surprising new escape channel for ultracold neutrons (UCNs) in traps was reported recently. It could be relevant to the long-standing puzzle of the “too high” loss rate of UCNs from traps, which has yet to be completely understood and eliminated. In the present work we positively identify the new phenomenon and investigate it in detail. The escape of UCNs from traps is due to rare events in which their energy undergoes a small increase (∼10 −7 eV). The reason for such an energy gain and its impact on the physics of UCN storage is still to be investigated.

Journal of Experimental and Theoretical Physics Letters•Aug 1, 1999•9 citations

Comment to the article "Temperature dependence of ultracold neutron loss rates" E.Korobkina et al., PRB 70,035409

Anatolii P. Serebrov

In work [1] ("Temperature dependence of ultracold neutron loss rates" E.Korobkina et al., PRB 70,035409) results of measurement of temperature dependence of losses of ultracold neutrons (UCN) in a range from 4 K to 300 K at UCN storage in a copper trap are presented. At interpretation of experimental data it was artificially considered only the difference of losses rate 1/tau(T)= 1/tau_exp(T)- 1/tau_exp(10K), (tau - UCN storage time in the trap). It has been accepted for temperature dependence of losses which changes from 0 to 3.3*10-4 per one collision of UCN with a trap surface. However, the analysis of raw experimental data shows that in a trap at temperature 10 K there is losses 1.0*10-3 per collision. They are considerably (in 3 times) more than discussed temperature dependence and almost 10 times more than losses due to capture cross section on copper. It is the most probable that these losses are connected with leakage of UCN through a slit of trap shutter. Change of the size of a slits on 25% at change of temperature from 300K to 10K can quite explain discussed temperature dependence. Certainly, hydrogen is present on a surface, but as it was shown at work [2] (V.P.Alfimenkov et al., JETP., Vol. 55, No. 2 25 Jan.1992) temperature dependence in 3 times lower, even on the undegased surfaces than on the degassed and deuterated surface in work [1]. At last, deuteration of a trap surface allows almost completely to suppress temperature dependence connected with presence of hydrogen [2]. The conclusion of work [1] is that hydrogen is localized on a surface in the form of a film, instead of distribution in the surface substance. This conclusion contradicts results of measurement of energy dependence of UCN losses in work [2]. More detailed analysis of work [1] and works [2] is presented below.

arXiv:0905.0803•May 6, 2009•0 citations

Storage of ultracold neutrons in a volume coated with diamondlike carbon

F. Atchison, B. Blau, M. Daum +17 more

Ultracold neutrons (UCN) with energy up to the Fermi potential were stored for the first time in a volume coated with diamondlike carbon. As a function of the UCN energy and wall temperature of the storage volume, we measured the wall loss parameter \ensuremath{\eta} and obtained $\ensuremath{\eta}=(3.1\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}4}$ at $T=290$ K and $\ensuremath{\eta}=(1.8\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}4}$ at $T=115$ K.

Physical Review C•Nov 9, 2006•31 citations

Neutron velocity distribution from a superthermal solid 2H2 ultracold neutron source

I. Altarev, M. Daum, A. Frei +13 more

The European Physical Journal A•Jul 1, 2008•25 citations
There is a longstanding dogma in the physics of ultracold neutrons (UCN): The optimal temperature of ortho-deuterium based UCN-sources must not exceed 5 K5\,\mathrm{K}5K. This value has been established by the pioneering work of Golub et al. decades ago, utilizing previously established cross sections for solid ortho-deuterium. But recently, an improved calculation of the crucial 1-phonon up-scattering cross section - using the so-called corrected Incoherent Approximation - leads to a new upper limit for the optimal operation temperature of ortho-deuterium based UCN sources. After a discussion of the relevant cross sections of the (\mathrm{D}_2)-molecule we conclude that the optimal temperature lies between 10 K10\,\mathrm{K}10K and 12 K12\,\mathrm{K}12K, a factor 2 higher than estimated earlier. This offers significantly relaxed cryogenic conditions for UCN experiments with solid ortho-deuterium and especially for the operation of ortho-deuterium based ultracold neutron sources.
Ultracold and very cold neutrons (UCN and VCN) interact strongly with nanoparticles due to the similarity of their wavelengths and nanoparticles sizes. We analyze the hypothesis that this interaction can provide efficient cooling of neutrons by ultracold nanoparticles at certain experimental conditions, thus increasing the density of UCN by many orders of magnitude. The present analytical and numerical description of the problem is limited to the model of independent nanoparticles at zero temperature. Constraints of application of this model are discussed.
The possibility of controlling the kinematic parameters of ultracold neutrons (UCNs) is analysed by the example of a waveguide transfer and transformation of 2D images in ultracold neutrons and by the example of an increase in the concentration and deceleration/acceleration of ultracold neutrons during their transport in the waveguide with a variable cross section. The critical parameters of the problem are estimated, which indicates both consistency of the proposed approach and the emerging experimental limitations.
A surprising new escape channel for ultracold neutrons (UCNs) in traps was reported recently. It could be relevant to the long-standing puzzle of the “too high” loss rate of UCNs from traps, which has yet to be completely understood and eliminated. In the present work we positively identify the new phenomenon and investigate it in detail. The escape of UCNs from traps is due to rare events in which their energy undergoes a small increase (∼10 −7 eV). The reason for such an energy gain and its impact on the physics of UCN storage is still to be investigated.
In work [1] ("Temperature dependence of ultracold neutron loss rates" E.Korobkina et al., PRB 70,035409) results of measurement of temperature dependence of losses of ultracold neutrons (UCN) in a range from 4 K to 300 K at UCN storage in a copper trap are presented. At interpretation of experimental data it was artificially considered only the difference of losses rate 1/tau(T)= 1/tau_exp(T)- 1/tau_exp(10K), (tau - UCN storage time in the trap). It has been accepted for temperature dependence of losses which changes from 0 to 3.3*10-4 per one collision of UCN with a trap surface. However, the analysis of raw experimental data shows that in a trap at temperature 10 K there is losses 1.0*10-3 per collision. They are considerably (in 3 times) more than discussed temperature dependence and almost 10 times more than losses due to capture cross section on copper. It is the most probable that these losses are connected with leakage of UCN through a slit of trap shutter. Change of the size of a slits on 25% at change of temperature from 300K to 10K can quite explain discussed temperature dependence. Certainly, hydrogen is present on a surface, but as it was shown at work [2] (V.P.Alfimenkov et al., JETP., Vol. 55, No. 2 25 Jan.1992) temperature dependence in 3 times lower, even on the undegased surfaces than on the degassed and deuterated surface in work [1]. At last, deuteration of a trap surface allows almost completely to suppress temperature dependence connected with presence of hydrogen [2]. The conclusion of work [1] is that hydrogen is localized on a surface in the form of a film, instead of distribution in the surface substance. This conclusion contradicts results of measurement of energy dependence of UCN losses in work [2]. More detailed analysis of work [1] and works [2] is presented below.
Ultracold neutrons (UCN) with energy up to the Fermi potential were stored for the first time in a volume coated with diamondlike carbon. As a function of the UCN energy and wall temperature of the storage volume, we measured the wall loss parameter \ensuremath{\eta} and obtained $\ensuremath{\eta}=(3.1\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}4}$ at T=290T=290T=290 K and $\ensuremath{\eta}=(1.8\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}4}$ at T=115T=115T=115 K.