Due to its small size, low weight, and low power consumption, the Rb atomic frequency standard (RAFS) is routinely the first choice for atomic timekeeping in space. Consequently, though the device has very good frequency stability (rivaling passive hydrogen masers), there is interest in uncovering the fundamental processes limiting its long-term performance, with the goal of improving the device for future space systems and missions. The ac Stark shift (i.e., light shift) is one of the more likely processes limiting the RAFS’ long-term timekeeping ability, yet its manifestation in the RAFS remains poorly understood. In part, this comes from the fact that light-shift induced frequency fluctuations must be quantified in terms of the RAFS’ light-shift coefficient and the output variations in the RAFS’ rf-discharge lamp, which is a nonlinear inductively-couple plasma (ICP). Here, we analyze the light-shift effect for a family of 10 on-orbit Block-IIR GPS RAFS, examining decade-long records of their on-orbit frequency and rf-discharge lamp fluctuations. We find that the ICP’s light intensity variations can take several forms: deterministic aging, jumps, ramps, and non-stationary noise, each of which affects the RAFS’ frequency via the light shift. Correlating these light intensity changes with RAFS frequency changes, we estimate the light-shift coefficient, jLS, for the family of RAFS: kLS=-(1.9+-0.3)x10^-12/%. The 16% family-wide variation in kLS indicates that while each RAFS may have its own individual kLS, the variance of kLS among similarly designed RAFS can be relatively small. Combining kLS with our estimate of the ICP light intensity’s non-stationary noise, we find evidence that random-walk frequency noise in high-quality space-borne RAFS is strongly influenced by the RAFS’ rf-discharge lamp via the light shift effect.

The ac stark shift and space-borne rubidium atomic clocks / Formichella, Valerio; Camparo, J.; Sesia, Ilaria; Signorile, Giovanna; Galleani, Lorenzo; Huang, M.; Tavella, Patrizia. - In: JOURNAL OF APPLIED PHYSICS. - ISSN 0021-8979. - ELETTRONICO. - 120:19(2016), pp. 1-10. [10.1063/1.4967787]

The ac stark shift and space-borne rubidium atomic clocks

FORMICHELLA, VALERIO;SESIA, ILARIA;SIGNORILE, GIOVANNA;GALLEANI, Lorenzo;TAVELLA, PATRIZIA
2016

Abstract

Due to its small size, low weight, and low power consumption, the Rb atomic frequency standard (RAFS) is routinely the first choice for atomic timekeeping in space. Consequently, though the device has very good frequency stability (rivaling passive hydrogen masers), there is interest in uncovering the fundamental processes limiting its long-term performance, with the goal of improving the device for future space systems and missions. The ac Stark shift (i.e., light shift) is one of the more likely processes limiting the RAFS’ long-term timekeeping ability, yet its manifestation in the RAFS remains poorly understood. In part, this comes from the fact that light-shift induced frequency fluctuations must be quantified in terms of the RAFS’ light-shift coefficient and the output variations in the RAFS’ rf-discharge lamp, which is a nonlinear inductively-couple plasma (ICP). Here, we analyze the light-shift effect for a family of 10 on-orbit Block-IIR GPS RAFS, examining decade-long records of their on-orbit frequency and rf-discharge lamp fluctuations. We find that the ICP’s light intensity variations can take several forms: deterministic aging, jumps, ramps, and non-stationary noise, each of which affects the RAFS’ frequency via the light shift. Correlating these light intensity changes with RAFS frequency changes, we estimate the light-shift coefficient, jLS, for the family of RAFS: kLS=-(1.9+-0.3)x10^-12/%. The 16% family-wide variation in kLS indicates that while each RAFS may have its own individual kLS, the variance of kLS among similarly designed RAFS can be relatively small. Combining kLS with our estimate of the ICP light intensity’s non-stationary noise, we find evidence that random-walk frequency noise in high-quality space-borne RAFS is strongly influenced by the RAFS’ rf-discharge lamp via the light shift effect.
File in questo prodotto:
File Dimensione Formato  
The ac stark shift and space-borne rubidium atomic clocks.pdf

accesso aperto

Descrizione: Articolo principale
Tipologia: 2. Post-print / Author's Accepted Manuscript
Licenza: PUBBLICO - Tutti i diritti riservati
Dimensione 2.67 MB
Formato Adobe PDF
2.67 MB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2658386
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo