Which factors prevent Israel from providing Kyiv with "Iron Dome" system?

Ukraine has been requesting the supply of more advanced military equipment, such as that of the US "Patriot" missile system and the renowned Israeli air defence system "Iron Dome". While US President Biden confirmed the request for Patriot systems to Ukraine during President Volodymyr Zelenskyy's recent visit to Washington, Israel is unlikely to follow suit. 

Jacob Nagel, a former Israeli National Security Advisor and now visiting Professor at the Aerospace faculty of the Technion – Israel Institute of Technology, wrote an article for the National Interest publication, providing an insight into what reasons prevent Israel from providing their air defence technology to Kyiv. 

"First and most important, Israel harbors legitimate fears that if any of its systems were to be deployed, they would be captured by Russia on the battlefield. From there, they are all but guaranteed to be sent to Iran for analysis. This analysis could enable the regime to find ways to counter these systems in the battlespaces where Iran’s proxies and Israel are squaring off. This would benefit Hezbollah, Hamas, and Palestinian Islamic Jihad in future confrontations with Israel", the security expert said. 

Further reasons for Tel Aviv's hesitance are that the Israel Defense Forces have assessed the urgent need for acquiring more weapons amid an increasing threat from Hezbollah and Hamas’ growing weapon arsenal. According to Nagel, the lengthy time needed to train Ukrainian troops on how to operate the Iron dome would not add any short-term benefits to Kyiv right now. 

He further pointed to Syria being another important factor in this calculation, stating that "Israel does not wish to trigger a harsh response from Russia, which maintains a significant presence in Syria, where Israel is engaged in regular kinetic activity to neutralize efforts by the Iranian regime to smuggle advanced weapons to Hezbollah in Lebanon. Recent reports indicate that Russia is withdrawing troops and systems, mainly air defenses, out of Syria. They cannot maintain Syrian systems because of a scarcity of spare parts, and they have declined to replenish the air defense systems destroyed by the Israeli Air Force".